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1 | <html> |
2 | <head> | |
3 | <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> | |
4 | <title>Detailed Semantics</title> | |
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24 | </div> | |
25 | <div class="section"> | |
26 | <div class="titlepage"><div><div><h4 class="title"> | |
27 | <a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics"></a><a class="link" href="detailed_semantics.html" title="Detailed Semantics">Detailed | |
28 | Semantics</a> | |
29 | </h4></div></div></div> | |
30 | <p> | |
31 | Because <code class="computeroutput"><span class="identifier">T</span></code> might be of reference | |
32 | type, in the sequel, those entries whose semantic depends on <code class="computeroutput"><span class="identifier">T</span></code> being of reference type or not will | |
33 | be distinguished using the following convention: | |
34 | </p> | |
35 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
36 | <li class="listitem"> | |
37 | If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code><span class="emphasis"><em>(not | |
38 | a ref)</em></span><code class="computeroutput"><span class="special">></span></code>, | |
39 | the description corresponds only to the case where <code class="computeroutput"><span class="identifier">T</span></code> | |
40 | is not of reference type. | |
41 | </li> | |
42 | <li class="listitem"> | |
43 | If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span></code>, the description corresponds | |
44 | only to the case where <code class="computeroutput"><span class="identifier">T</span></code> | |
45 | is of reference type. | |
46 | </li> | |
47 | <li class="listitem"> | |
48 | If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>, the description is the same for | |
49 | both cases. | |
50 | </li> | |
51 | </ul></div> | |
52 | <div class="note"><table border="0" summary="Note"> | |
53 | <tr> | |
54 | <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td> | |
55 | <th align="left">Note</th> | |
56 | </tr> | |
57 | <tr><td align="left" valign="top"><p> | |
58 | The following section contains various <code class="computeroutput"><span class="identifier">assert</span><span class="special">()</span></code> which are used only to show the postconditions | |
59 | as sample code. It is not implied that the type <code class="computeroutput"><span class="identifier">T</span></code> | |
60 | must support each particular expression but that if the expression is | |
61 | supported, the implied condition holds. | |
62 | </p></td></tr> | |
63 | </table></div> | |
64 | <p> | |
65 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
66 | </p> | |
67 | <h6> | |
68 | <a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.h0"></a> | |
69 | <span class="phrase"><a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.optional_class_member_functions"></a></span><a class="link" href="detailed_semantics.html#boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.optional_class_member_functions">optional | |
70 | class member functions</a> | |
71 | </h6> | |
72 | <p> | |
73 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
74 | </p> | |
75 | <a name="reference_optional_constructor"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
76 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span> | |
77 | <span class="keyword">noexcept</span><span class="special">;</span></code> | |
78 | </p></blockquote></div> | |
79 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
80 | <li class="listitem"> | |
81 | <span class="bold"><strong>Effect:</strong></span> Default-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. | |
82 | </li> | |
83 | <li class="listitem"> | |
84 | <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>. | |
85 | </li> | |
86 | <li class="listitem"> | |
87 | <span class="bold"><strong>Notes:</strong></span> T's default constructor <span class="underline">is not</span> called. | |
88 | </li> | |
89 | <li class="listitem"> | |
90 | <span class="bold"><strong>Example:</strong></span> | |
91 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> | |
92 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span> | |
93 | </pre> | |
94 | </li> | |
95 | </ul></div> | |
96 | <p> | |
97 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
98 | </p> | |
99 | <a name="reference_optional_constructor_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
100 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> | |
101 | <span class="identifier">none_t</span> <span class="special">)</span> | |
102 | <span class="keyword">noexcept</span><span class="special">;</span></code> | |
103 | </p></blockquote></div> | |
104 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
105 | <li class="listitem"> | |
106 | <span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code> uninitialized. | |
107 | </li> | |
108 | <li class="listitem"> | |
109 | <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>. | |
110 | </li> | |
111 | <li class="listitem"> | |
112 | <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>'s | |
113 | default constructor <span class="underline">is not</span> called. | |
114 | The expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code> | |
115 | denotes an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none_t</span></code> | |
116 | that can be used as the parameter. | |
117 | </li> | |
118 | <li class="listitem"> | |
119 | <span class="bold"><strong>Example:</strong></span> | |
120 | <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">none</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> | |
121 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">n</span><span class="special">(</span><span class="identifier">none</span><span class="special">)</span> <span class="special">;</span> | |
122 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">n</span> <span class="special">)</span> <span class="special">;</span> | |
123 | </pre> | |
124 | </li> | |
125 | </ul></div> | |
126 | <p> | |
127 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
128 | </p> | |
129 | <a name="reference_optional_constructor_value"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
130 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code> | |
131 | </p></blockquote></div> | |
132 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
133 | <li class="listitem"> | |
134 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code> | |
135 | is <code class="computeroutput"><span class="keyword">true</span></code>. | |
136 | </li> | |
137 | <li class="listitem"> | |
138 | <span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. | |
139 | </li> | |
140 | <li class="listitem"> | |
141 | <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span> | |
142 | and its value is a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">v</span></code>. | |
143 | </li> | |
144 | <li class="listitem"> | |
145 | <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> | |
146 | <span class="special">)</span></code> throws. | |
147 | </li> | |
148 | <li class="listitem"> | |
149 | <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> | |
150 | <span class="special">)</span></code> is called. | |
151 | </li> | |
152 | <li class="listitem"> | |
153 | <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only | |
154 | be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> | |
155 | <span class="special">);</span></code> in that case, this constructor | |
156 | has no effect. | |
157 | </li> | |
158 | <li class="listitem"> | |
159 | <span class="bold"><strong>Example:</strong></span> | |
160 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> | |
161 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> | |
162 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
163 | </pre> | |
164 | </li> | |
165 | </ul></div> | |
166 | <p> | |
167 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
168 | </p> | |
169 | <div class="blockquote"><blockquote class="blockquote"><p> | |
170 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> | |
171 | <span class="identifier">T</span><span class="special">&</span> | |
172 | <span class="identifier">ref</span> <span class="special">)</span></code> | |
173 | </p></blockquote></div> | |
174 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
175 | <li class="listitem"> | |
176 | <span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. | |
177 | </li> | |
178 | <li class="listitem"> | |
179 | <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span> | |
180 | and its value is an instance of an internal type wrapping the reference | |
181 | <code class="computeroutput"><span class="identifier">ref</span></code>. | |
182 | </li> | |
183 | <li class="listitem"> | |
184 | <span class="bold"><strong>Throws:</strong></span> Nothing. | |
185 | </li> | |
186 | <li class="listitem"> | |
187 | <span class="bold"><strong>Example:</strong></span> | |
188 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> | |
189 | <span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span> | |
190 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">vref</span><span class="special">);</span> | |
191 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
192 | <span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span> <span class="comment">// mutate referee</span> | |
193 | <span class="identifier">assert</span> <span class="special">(*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span><span class="special">);</span> | |
194 | </pre> | |
195 | </li> | |
196 | </ul></div> | |
197 | <p> | |
198 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
199 | </p> | |
200 | <a name="reference_optional_constructor_move_value"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
201 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">v</span> | |
202 | <span class="special">)</span></code> | |
203 | </p></blockquote></div> | |
204 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
205 | <li class="listitem"> | |
206 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code> | |
207 | is <code class="computeroutput"><span class="keyword">true</span></code>. | |
208 | </li> | |
209 | <li class="listitem"> | |
210 | <span class="bold"><strong>Effect:</strong></span> Directly-Move-Constructs an | |
211 | <code class="computeroutput"><span class="identifier">optional</span></code>. | |
212 | </li> | |
213 | <li class="listitem"> | |
214 | <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span> | |
215 | and its value is move-constructed from <code class="computeroutput"><span class="identifier">v</span></code>. | |
216 | </li> | |
217 | <li class="listitem"> | |
218 | <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code> | |
219 | throws. | |
220 | </li> | |
221 | <li class="listitem"> | |
222 | <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code> | |
223 | is called. | |
224 | </li> | |
225 | <li class="listitem"> | |
226 | <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only | |
227 | be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code> | |
228 | in that case, the state of <code class="computeroutput"><span class="identifier">v</span></code> | |
229 | is determined by exception safety guarantees for <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>. | |
230 | </li> | |
231 | <li class="listitem"> | |
232 | <span class="bold"><strong>Example:</strong></span> | |
233 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v1</span><span class="special">,</span> <span class="identifier">v2</span><span class="special">;</span> | |
234 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">v1</span><span class="special">));</span> | |
235 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v2</span> <span class="special">)</span> <span class="special">;</span> | |
236 | </pre> | |
237 | </li> | |
238 | </ul></div> | |
239 | <p> | |
240 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
241 | </p> | |
242 | <div class="blockquote"><blockquote class="blockquote"><p> | |
243 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> | |
244 | <span class="identifier">T</span><span class="special">&&</span> | |
245 | <span class="identifier">ref</span> <span class="special">)</span> | |
246 | <span class="special">=</span> <span class="keyword">delete</span></code> | |
247 | </p></blockquote></div> | |
248 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
249 | <span class="bold"><strong>Notes:</strong></span> This constructor is deleted | |
250 | </li></ul></div> | |
251 | <p> | |
252 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
253 | </p> | |
254 | <a name="reference_optional_constructor_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
255 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> | |
256 | <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code> | |
257 | </p></blockquote></div> | |
258 | <div class="blockquote"><blockquote class="blockquote"><p> | |
259 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> | |
260 | <span class="special">::</span><span class="identifier">optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> | |
261 | <span class="identifier">T</span><span class="special">&</span> | |
262 | <span class="identifier">v</span> <span class="special">)</span> | |
263 | <span class="special">;</span></code> | |
264 | </p></blockquote></div> | |
265 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
266 | If condition is true, same as: | |
267 | </li></ul></div> | |
268 | <div class="blockquote"><blockquote class="blockquote"><p> | |
269 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code> | |
270 | </p></blockquote></div> | |
271 | <div class="blockquote"><blockquote class="blockquote"><p> | |
272 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> | |
273 | <span class="special">::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code> | |
274 | </p></blockquote></div> | |
275 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
276 | otherwise, same as: | |
277 | </li></ul></div> | |
278 | <div class="blockquote"><blockquote class="blockquote"><p> | |
279 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span></code> | |
280 | </p></blockquote></div> | |
281 | <div class="blockquote"><blockquote class="blockquote"><p> | |
282 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> | |
283 | <span class="special">::</span><span class="identifier">optional</span><span class="special">()</span></code> | |
284 | </p></blockquote></div> | |
285 | <p> | |
286 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
287 | </p> | |
288 | <a name="reference_optional_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
289 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span> | |
290 | <span class="keyword">const</span><span class="special">&</span> | |
291 | <span class="identifier">rhs</span> <span class="special">);</span></code> | |
292 | </p></blockquote></div> | |
293 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
294 | <li class="listitem"> | |
295 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code> | |
296 | is <code class="computeroutput"><span class="keyword">true</span></code>. | |
297 | </li> | |
298 | <li class="listitem"> | |
299 | <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. | |
300 | </li> | |
301 | <li class="listitem"> | |
302 | <span class="bold"><strong>Postconditions:</strong></span> If rhs is initialized, | |
303 | <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
304 | is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the | |
305 | value of <code class="computeroutput"><span class="identifier">rhs</span></code>; else | |
306 | <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
307 | is uninitialized. | |
308 | </li> | |
309 | <li class="listitem"> | |
310 | <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> | |
311 | <span class="special">)</span></code> throws. | |
312 | </li> | |
313 | <li class="listitem"> | |
314 | <span class="bold"><strong>Notes:</strong></span> If rhs is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code> | |
315 | is called. | |
316 | </li> | |
317 | <li class="listitem"> | |
318 | <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only | |
319 | be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> | |
320 | <span class="special">);</span></code> in that case, this constructor | |
321 | has no effect. | |
322 | </li> | |
323 | <li class="listitem"> | |
324 | <span class="bold"><strong>Example:</strong></span> | |
325 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uninit</span> <span class="special">;</span> | |
326 | <span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span> | |
327 | ||
328 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span> | |
329 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span> | |
330 | ||
331 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">);</span> | |
332 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
333 | ||
334 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span> | |
335 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span> | |
336 | </pre> | |
337 | </li> | |
338 | </ul></div> | |
339 | <p> | |
340 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
341 | </p> | |
342 | <div class="blockquote"><blockquote class="blockquote"><p> | |
343 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> | |
344 | <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> | |
345 | <span class="special">);</span></code> | |
346 | </p></blockquote></div> | |
347 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
348 | <li class="listitem"> | |
349 | <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. | |
350 | </li> | |
351 | <li class="listitem"> | |
352 | <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> | |
353 | is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
354 | is initialized and its value is another reference to the same object | |
355 | referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>; | |
356 | else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
357 | is uninitialized. | |
358 | </li> | |
359 | <li class="listitem"> | |
360 | <span class="bold"><strong>Throws:</strong></span> Nothing. | |
361 | </li> | |
362 | <li class="listitem"> | |
363 | <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> | |
364 | is initialized, both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> will refer to the same object | |
365 | (they alias). | |
366 | </li> | |
367 | <li class="listitem"> | |
368 | <span class="bold"><strong>Example:</strong></span> | |
369 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uninit</span> <span class="special">;</span> | |
370 | <span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span> | |
371 | ||
372 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span> | |
373 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span> | |
374 | ||
375 | <span class="identifier">T</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">ref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span> | |
376 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">ref</span><span class="special">);</span> | |
377 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
378 | ||
379 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span> | |
380 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
381 | ||
382 | <span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span> | |
383 | ||
384 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span> | |
385 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span> | |
386 | </pre> | |
387 | </li> | |
388 | </ul></div> | |
389 | <p> | |
390 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
391 | </p> | |
392 | <a name="reference_optional_move_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
393 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span> | |
394 | <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code> | |
395 | </p></blockquote></div> | |
396 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
397 | <li class="listitem"> | |
398 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code> | |
399 | is <code class="computeroutput"><span class="keyword">true</span></code>. | |
400 | </li> | |
401 | <li class="listitem"> | |
402 | <span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. | |
403 | </li> | |
404 | <li class="listitem"> | |
405 | <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> | |
406 | is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
407 | is initialized and its value is move constructed from <code class="computeroutput"><span class="identifier">rhs</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized. | |
408 | </li> | |
409 | <li class="listitem"> | |
410 | <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code> | |
411 | throws. | |
412 | </li> | |
413 | <li class="listitem"> | |
414 | <span class="bold"><strong>Remarks:</strong></span> The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code> is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>. | |
415 | </li> | |
416 | <li class="listitem"> | |
417 | <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> | |
418 | is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="special">&&</span> | |
419 | <span class="special">)</span></code> is called. | |
420 | </li> | |
421 | <li class="listitem"> | |
422 | <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only | |
423 | be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code> | |
424 | in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains | |
425 | initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety | |
426 | of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>. | |
427 | </li> | |
428 | <li class="listitem"> | |
429 | <span class="bold"><strong>Example:</strong></span> | |
430 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uninit</span> <span class="special">;</span> | |
431 | <span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span> | |
432 | ||
433 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
434 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span> | |
435 | ||
436 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">uniqye_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">);</span> | |
437 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
438 | ||
439 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
440 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">);</span> | |
441 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="keyword">nullptr</span> <span class="special">);</span> | |
442 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">);</span> | |
443 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
444 | </pre> | |
445 | </li> | |
446 | </ul></div> | |
447 | <p> | |
448 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
449 | </p> | |
450 | <div class="blockquote"><blockquote class="blockquote"><p> | |
451 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span> | |
452 | <span class="identifier">optional</span> <span class="special">&&</span> | |
453 | <span class="identifier">rhs</span> <span class="special">);</span></code> | |
454 | </p></blockquote></div> | |
455 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
456 | <li class="listitem"> | |
457 | <span class="bold"><strong>Effect:</strong></span> Move-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. | |
458 | </li> | |
459 | <li class="listitem"> | |
460 | <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> | |
461 | is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
462 | is initialized and its value is another reference to the same object | |
463 | referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>; | |
464 | else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
465 | is uninitialized. | |
466 | </li> | |
467 | <li class="listitem"> | |
468 | <span class="bold"><strong>Throws:</strong></span> Nothing. | |
469 | </li> | |
470 | <li class="listitem"> | |
471 | <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> | |
472 | is initialized, both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> will refer to the same object | |
473 | (they alias). | |
474 | </li> | |
475 | <li class="listitem"> | |
476 | <span class="bold"><strong>Example:</strong></span> | |
477 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uninit</span> <span class="special">;</span> | |
478 | <span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span> | |
479 | ||
480 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
481 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span> | |
482 | ||
483 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">v</span><span class="special">(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span> | |
484 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> | |
485 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
486 | ||
487 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
488 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
489 | ||
490 | <span class="special">*</span><span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span> | |
491 | ||
492 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span> | |
493 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span> | |
494 | </pre> | |
495 | </li> | |
496 | </ul></div> | |
497 | <p> | |
498 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
499 | </p> | |
500 | <a name="reference_optional_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
501 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
502 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> | |
503 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">);</span></code> | |
504 | </p></blockquote></div> | |
505 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
506 | <li class="listitem"> | |
507 | <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. | |
508 | </li> | |
509 | <li class="listitem"> | |
510 | <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> | |
511 | is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
512 | is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the | |
513 | value of rhs converted to type <code class="computeroutput"><span class="identifier">T</span></code>; | |
514 | else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
515 | is uninitialized. | |
516 | </li> | |
517 | <li class="listitem"> | |
518 | <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span> | |
519 | <span class="special">)</span></code> throws. | |
520 | </li> | |
521 | <li class="listitem"> | |
522 | <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span> | |
523 | <span class="special">)</span></code> is called if <code class="computeroutput"><span class="identifier">rhs</span></code> is initialized, which requires | |
524 | a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code> | |
525 | to <code class="computeroutput"><span class="identifier">T</span></code>. | |
526 | </li> | |
527 | <li class="listitem"> | |
528 | <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only | |
529 | be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span> | |
530 | <span class="special">);</span></code> in that case, this constructor | |
531 | has no effect. | |
532 | </li> | |
533 | <li class="listitem"> | |
534 | <span class="bold"><strong>Example:</strong></span> | |
535 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span> | |
536 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span> | |
537 | ||
538 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span> | |
539 | <span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span> | |
540 | </pre> | |
541 | </li> | |
542 | </ul></div> | |
543 | <p> | |
544 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
545 | </p> | |
546 | <a name="reference_optional_move_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
547 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
548 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> | |
549 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> | |
550 | <span class="identifier">rhs</span> <span class="special">);</span></code> | |
551 | </p></blockquote></div> | |
552 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
553 | <li class="listitem"> | |
554 | <span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>. | |
555 | </li> | |
556 | <li class="listitem"> | |
557 | <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code> | |
558 | is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
559 | is initialized and its value is move-constructed from <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>; | |
560 | else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
561 | is uninitialized. | |
562 | </li> | |
563 | <li class="listitem"> | |
564 | <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code> | |
565 | throws. | |
566 | </li> | |
567 | <li class="listitem"> | |
568 | <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code> | |
569 | is called if <code class="computeroutput"><span class="identifier">rhs</span></code> is | |
570 | initialized, which requires a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code> | |
571 | to <code class="computeroutput"><span class="identifier">T</span></code>. | |
572 | </li> | |
573 | <li class="listitem"> | |
574 | <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only | |
575 | be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">);</span></code> | |
576 | in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains | |
577 | initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety | |
578 | guarantee of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> | |
579 | <span class="special">)</span></code>. | |
580 | </li> | |
581 | <li class="listitem"> | |
582 | <span class="bold"><strong>Example:</strong></span> | |
583 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span> | |
584 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span> | |
585 | ||
586 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">x</span><span class="special">))</span> <span class="special">;</span> | |
587 | <span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span> | |
588 | </pre> | |
589 | </li> | |
590 | </ul></div> | |
591 | <p> | |
592 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
593 | </p> | |
594 | <a name="reference_optional_constructor_factory"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
595 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span> | |
596 | <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
597 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> | |
598 | <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code> | |
599 | </p></blockquote></div> | |
600 | <div class="blockquote"><blockquote class="blockquote"><p> | |
601 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span> | |
602 | <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
603 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> | |
604 | <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code> | |
605 | </p></blockquote></div> | |
606 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
607 | <li class="listitem"> | |
608 | <span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code> with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained from the factory. | |
609 | </li> | |
610 | <li class="listitem"> | |
611 | <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span> | |
612 | and its value is <span class="emphasis"><em>directly given</em></span> from the factory | |
613 | <code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value | |
614 | <span class="underline">is not copied</span>). | |
615 | </li> | |
616 | <li class="listitem"> | |
617 | <span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code> constructor called by the factory | |
618 | throws. | |
619 | </li> | |
620 | <li class="listitem"> | |
621 | <span class="bold"><strong>Notes:</strong></span> See <a class="link" href="../../tutorial/in_place_factories.html" title="In-Place Factories">In-Place | |
622 | Factories</a> | |
623 | </li> | |
624 | <li class="listitem"> | |
625 | <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only | |
626 | be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code> | |
627 | constructor used by the factory; in that case, this constructor has | |
628 | no effect. | |
629 | </li> | |
630 | <li class="listitem"> | |
631 | <span class="bold"><strong>Example:</strong></span> | |
632 | <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">C</span> <span class="special">{</span> <span class="identifier">C</span> <span class="special">(</span> <span class="keyword">char</span><span class="special">,</span> <span class="keyword">double</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">)</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span> | |
633 | ||
634 | <span class="identifier">C</span> <span class="identifier">v</span><span class="special">(</span><span class="char">'A'</span><span class="special">,</span><span class="number">123.4</span><span class="special">,</span><span class="string">"hello"</span><span class="special">);</span> | |
635 | ||
636 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span> <span class="identifier">in_place</span> <span class="special">(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// InPlaceFactory used</span> | |
637 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span> <span class="identifier">in_place</span><span class="special"><</span><span class="identifier">C</span><span class="special">>(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// TypedInPlaceFactory used</span> | |
638 | ||
639 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
640 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
641 | </pre> | |
642 | </li> | |
643 | </ul></div> | |
644 | <p> | |
645 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
646 | </p> | |
647 | <a name="reference_optional_operator_equal_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
648 | <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span> | |
649 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> | |
650 | <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code> | |
651 | </p></blockquote></div> | |
652 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
653 | <li class="listitem"> | |
654 | <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized destroys its contained | |
655 | value. | |
656 | </li> | |
657 | <li class="listitem"> | |
658 | <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized. | |
659 | </li> | |
660 | </ul></div> | |
661 | <p> | |
662 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
663 | </p> | |
664 | <a name="reference_optional_operator_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
665 | <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span> | |
666 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span> | |
667 | <span class="keyword">const</span><span class="special">&</span> | |
668 | <span class="identifier">rhs</span> <span class="special">)</span> | |
669 | <span class="special">;</span></code> | |
670 | </p></blockquote></div> | |
671 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
672 | <li class="listitem"> | |
673 | <span class="bold"><strong>Effect:</strong></span> Assigns the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>. | |
674 | </li> | |
675 | <li class="listitem"> | |
676 | <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is | |
677 | a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">rhs</span></code>. | |
678 | </li> | |
679 | <li class="listitem"> | |
680 | <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> | |
681 | <span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&)</span></code> | |
682 | throws. | |
683 | </li> | |
684 | <li class="listitem"> | |
685 | <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s assignment operator is used, | |
686 | otherwise, its copy-constructor is used. | |
687 | </li> | |
688 | <li class="listitem"> | |
689 | <span class="bold"><strong>Exception Safety:</strong></span> In the event of | |
690 | an exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified | |
691 | as far as <code class="computeroutput"><span class="identifier">optional</span></code> | |
692 | is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s | |
693 | <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>). | |
694 | If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
695 | is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s | |
696 | <span class="emphasis"><em>copy constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized. | |
697 | </li> | |
698 | <li class="listitem"> | |
699 | <span class="bold"><strong>Example:</strong></span> | |
700 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span> | |
701 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> | |
702 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span> | |
703 | ||
704 | <span class="identifier">T</span> <span class="identifier">y</span><span class="special">;</span> | |
705 | <span class="identifier">def</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span> | |
706 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> | |
707 | <span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span> | |
708 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span> | |
709 | </pre> | |
710 | </li> | |
711 | </ul></div> | |
712 | <p> | |
713 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
714 | </p> | |
715 | <div class="blockquote"><blockquote class="blockquote"><p> | |
716 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> | |
717 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">rhs</span> | |
718 | <span class="special">)</span> <span class="special">;</span></code> | |
719 | </p></blockquote></div> | |
720 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
721 | <li class="listitem"> | |
722 | <span class="bold"><strong>Effect:</strong></span> (Re)binds the wrapped reference. | |
723 | </li> | |
724 | <li class="listitem"> | |
725 | <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and it references | |
726 | the same object referenced by <code class="computeroutput"><span class="identifier">rhs</span></code>. | |
727 | </li> | |
728 | <li class="listitem"> | |
729 | <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, it is <span class="emphasis"><em>rebound</em></span> | |
730 | to the new object. See <a class="link" href="../../tutorial/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a> | |
731 | for details on this behavior. | |
732 | </li> | |
733 | <li class="listitem"> | |
734 | <span class="bold"><strong>Example:</strong></span> | |
735 | <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span> | |
736 | <span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> | |
737 | <span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span> | |
738 | <span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span> | |
739 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span> | |
740 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span> | |
741 | ||
742 | <span class="identifier">def</span> <span class="special">=</span> <span class="identifier">rb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb'</span> | |
743 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span> | |
744 | <span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span> | |
745 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span> | |
746 | <span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span> | |
747 | <span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span> | |
748 | <span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">rc</span> <span class="special">;</span> <span class="comment">// REBINDS to 'c' through 'rc'</span> | |
749 | <span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span> | |
750 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span> | |
751 | </pre> | |
752 | </li> | |
753 | </ul></div> | |
754 | <p> | |
755 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
756 | </p> | |
757 | <a name="reference_optional_operator_move_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
758 | <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span> | |
759 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">rhs</span> | |
760 | <span class="special">)</span> <span class="special">;</span></code> | |
761 | </p></blockquote></div> | |
762 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
763 | <li class="listitem"> | |
764 | <span class="bold"><strong>Effect:</strong></span> Moves the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>. | |
765 | </li> | |
766 | <li class="listitem"> | |
767 | <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is | |
768 | moved from <code class="computeroutput"><span class="identifier">rhs</span></code>. | |
769 | </li> | |
770 | <li class="listitem"> | |
771 | <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code> | |
772 | or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="special">&&)</span></code> | |
773 | throws. | |
774 | </li> | |
775 | <li class="listitem"> | |
776 | <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s move-assignment operator is used, | |
777 | otherwise, its move-constructor is used. | |
778 | </li> | |
779 | <li class="listitem"> | |
780 | <span class="bold"><strong>Exception Safety:</strong></span> In the event of | |
781 | an exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified | |
782 | as far as <code class="computeroutput"><span class="identifier">optional</span></code> | |
783 | is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s | |
784 | <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>). | |
785 | If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
786 | is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s | |
787 | <span class="emphasis"><em>move constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized. | |
788 | </li> | |
789 | <li class="listitem"> | |
790 | <span class="bold"><strong>Example:</strong></span> | |
791 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span> | |
792 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> | |
793 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span> | |
794 | ||
795 | <span class="identifier">T</span> <span class="identifier">y1</span><span class="special">,</span> <span class="identifier">y2</span><span class="special">,</span> <span class="identifier">yR</span><span class="special">;</span> | |
796 | <span class="identifier">def</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y1</span><span class="special">)</span> <span class="special">;</span> | |
797 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span> | |
798 | <span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y2</span><span class="special">)</span> <span class="special">;</span> | |
799 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span> | |
800 | </pre> | |
801 | </li> | |
802 | </ul></div> | |
803 | <p> | |
804 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
805 | </p> | |
806 | <div class="blockquote"><blockquote class="blockquote"><p> | |
807 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> | |
808 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">rhs</span> | |
809 | <span class="special">)</span> <span class="special">=</span> | |
810 | <span class="keyword">delete</span><span class="special">;</span></code> | |
811 | </p></blockquote></div> | |
812 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
813 | <span class="bold"><strong>Notes:</strong></span> This assignment operator is | |
814 | deleted. | |
815 | </li></ul></div> | |
816 | <p> | |
817 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
818 | </p> | |
819 | <a name="reference_optional_operator_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
820 | <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span> | |
821 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span> | |
822 | <span class="keyword">const</span><span class="special">&</span> | |
823 | <span class="identifier">rhs</span> <span class="special">)</span> | |
824 | <span class="special">;</span></code> | |
825 | </p></blockquote></div> | |
826 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
827 | <li class="listitem"> | |
828 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> | |
829 | is <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> and <code class="computeroutput"><span class="identifier">CopyAssignable</span></code>. | |
830 | </li> | |
831 | <li class="listitem"> | |
832 | <p class="simpara"> | |
833 | <span class="bold"><strong>Effects:</strong></span> | |
834 | </p> | |
835 | <div class="informaltable"><table class="table"> | |
836 | <colgroup> | |
837 | <col> | |
838 | <col> | |
839 | <col> | |
840 | </colgroup> | |
841 | <thead><tr></tr></thead> | |
842 | <tbody> | |
843 | <tr> | |
844 | <td> | |
845 | </td> | |
846 | <td> | |
847 | <p> | |
848 | <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span> | |
849 | </p> | |
850 | </td> | |
851 | <td> | |
852 | <p> | |
853 | <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span> | |
854 | </p> | |
855 | </td> | |
856 | </tr> | |
857 | <tr> | |
858 | <td> | |
859 | <p> | |
860 | <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code> | |
861 | contains a value</strong></span> | |
862 | </p> | |
863 | </td> | |
864 | <td> | |
865 | <p> | |
866 | assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> | |
867 | to the contained value | |
868 | </p> | |
869 | </td> | |
870 | <td> | |
871 | <p> | |
872 | initializes the contained value as if direct-initializing | |
873 | an object of type <code class="computeroutput"><span class="identifier">T</span></code> | |
874 | with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> | |
875 | </p> | |
876 | </td> | |
877 | </tr> | |
878 | <tr> | |
879 | <td> | |
880 | <p> | |
881 | <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code> | |
882 | does not contain a value</strong></span> | |
883 | </p> | |
884 | </td> | |
885 | <td> | |
886 | <p> | |
887 | destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code> | |
888 | </p> | |
889 | </td> | |
890 | <td> | |
891 | <p> | |
892 | no effect | |
893 | </p> | |
894 | </td> | |
895 | </tr> | |
896 | </tbody> | |
897 | </table></div> | |
898 | </li> | |
899 | <li class="listitem"> | |
900 | <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>; | |
901 | </li> | |
902 | <li class="listitem"> | |
903 | <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>. | |
904 | </li> | |
905 | <li class="listitem"> | |
906 | <span class="bold"><strong>Exception Safety:</strong></span> If any exception | |
907 | is thrown, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code> | |
908 | remains unchanged. If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s copy constructor, no effect. | |
909 | If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s | |
910 | copy assignment, the state of its contained value is as defined by | |
911 | the exception safety guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s | |
912 | copy assignment. | |
913 | </li> | |
914 | <li class="listitem"> | |
915 | <span class="bold"><strong>Example:</strong></span> | |
916 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> | |
917 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> | |
918 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> | |
919 | ||
920 | <span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span> | |
921 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span> | |
922 | <span class="comment">// previous value (copy of 'v') destroyed from within 'opt'.</span> | |
923 | </pre> | |
924 | </li> | |
925 | </ul></div> | |
926 | <p> | |
927 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
928 | </p> | |
929 | <div class="blockquote"><blockquote class="blockquote"><p> | |
930 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> | |
931 | <span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> | |
932 | <span class="special">)</span> <span class="special">;</span></code> | |
933 | </p></blockquote></div> | |
934 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
935 | <li class="listitem"> | |
936 | <span class="bold"><strong>Effect:</strong></span> (Re)binds thee wrapped reference. | |
937 | </li> | |
938 | <li class="listitem"> | |
939 | <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
940 | is initialized and it references the same object referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>; | |
941 | otherwise, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
942 | is uninitialized (and references no object). | |
943 | </li> | |
944 | <li class="listitem"> | |
945 | <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized and so is <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>, | |
946 | <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
947 | is <span class="emphasis"><em>rebound</em></span> to the new object. See <a class="link" href="../../tutorial/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a> | |
948 | for details on this behavior. | |
949 | </li> | |
950 | <li class="listitem"> | |
951 | <span class="bold"><strong>Example:</strong></span> | |
952 | <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span> | |
953 | <span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> | |
954 | <span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span> | |
955 | <span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span> | |
956 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span> | |
957 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">ora</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span> | |
958 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orb</span><span class="special">(</span><span class="identifier">rb</span><span class="special">)</span> <span class="special">;</span> | |
959 | ||
960 | <span class="identifier">def</span> <span class="special">=</span> <span class="identifier">orb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb' wrapped within 'orb'</span> | |
961 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span> | |
962 | <span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">ora</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span> | |
963 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span> | |
964 | <span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span> | |
965 | <span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span> | |
966 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orc</span><span class="special">(</span><span class="identifier">rc</span><span class="special">)</span> <span class="special">;</span> | |
967 | <span class="identifier">ora</span> <span class="special">=</span> <span class="identifier">orc</span> <span class="special">;</span> <span class="comment">// REBINDS ora to 'c' through 'rc'</span> | |
968 | <span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span> | |
969 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">ora</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span> | |
970 | </pre> | |
971 | </li> | |
972 | </ul></div> | |
973 | <p> | |
974 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
975 | </p> | |
976 | <a name="reference_optional_operator_move_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
977 | <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span> | |
978 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span> | |
979 | <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code> | |
980 | </p></blockquote></div> | |
981 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
982 | <li class="listitem"> | |
983 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> | |
984 | is <code class="computeroutput"><span class="identifier">MoveConstructible</span></code> | |
985 | and <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>. | |
986 | </li> | |
987 | <li class="listitem"> | |
988 | <p class="simpara"> | |
989 | <span class="bold"><strong>Effects:</strong></span> | |
990 | </p> | |
991 | <div class="informaltable"><table class="table"> | |
992 | <colgroup> | |
993 | <col> | |
994 | <col> | |
995 | <col> | |
996 | </colgroup> | |
997 | <thead><tr></tr></thead> | |
998 | <tbody> | |
999 | <tr> | |
1000 | <td> | |
1001 | </td> | |
1002 | <td> | |
1003 | <p> | |
1004 | <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span> | |
1005 | </p> | |
1006 | </td> | |
1007 | <td> | |
1008 | <p> | |
1009 | <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span> | |
1010 | </p> | |
1011 | </td> | |
1012 | </tr> | |
1013 | <tr> | |
1014 | <td> | |
1015 | <p> | |
1016 | <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code> | |
1017 | contains a value</strong></span> | |
1018 | </p> | |
1019 | </td> | |
1020 | <td> | |
1021 | <p> | |
1022 | assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value | |
1023 | </p> | |
1024 | </td> | |
1025 | <td> | |
1026 | <p> | |
1027 | initializes the contained value as if direct-initializing | |
1028 | an object of type <code class="computeroutput"><span class="identifier">T</span></code> | |
1029 | with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> | |
1030 | </p> | |
1031 | </td> | |
1032 | </tr> | |
1033 | <tr> | |
1034 | <td> | |
1035 | <p> | |
1036 | <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code> | |
1037 | does not contain a value</strong></span> | |
1038 | </p> | |
1039 | </td> | |
1040 | <td> | |
1041 | <p> | |
1042 | destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code> | |
1043 | </p> | |
1044 | </td> | |
1045 | <td> | |
1046 | <p> | |
1047 | no effect | |
1048 | </p> | |
1049 | </td> | |
1050 | </tr> | |
1051 | </tbody> | |
1052 | </table></div> | |
1053 | </li> | |
1054 | <li class="listitem"> | |
1055 | <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>; | |
1056 | </li> | |
1057 | <li class="listitem"> | |
1058 | <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>. | |
1059 | </li> | |
1060 | <li class="listitem"> | |
1061 | <span class="bold"><strong>Remarks:</strong></span> The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code> is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span> <span class="special">&&</span> | |
1062 | <span class="identifier">is_nothrow_move_assignable</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>. | |
1063 | </li> | |
1064 | <li class="listitem"> | |
1065 | <span class="bold"><strong>Exception Safety:</strong></span> If any exception | |
1066 | is thrown, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code> | |
1067 | remains unchanged. If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s move constructor, the state of | |
1068 | <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> | |
1069 | is determined by the exception safety guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s | |
1070 | move constructor. If an exception is thrown during the call to T's | |
1071 | move-assignment, the state of <code class="computeroutput"><span class="special">**</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by the exception | |
1072 | safety guarantee of T's move assignment. | |
1073 | </li> | |
1074 | <li class="listitem"> | |
1075 | <span class="bold"><strong>Example:</strong></span> | |
1076 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span> | |
1077 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> | |
1078 | ||
1079 | <span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span> | |
1080 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span> | |
1081 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> | |
1082 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
1083 | </pre> | |
1084 | </li> | |
1085 | </ul></div> | |
1086 | <p> | |
1087 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1088 | </p> | |
1089 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1090 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> | |
1091 | <span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&&</span> <span class="identifier">rhs</span> | |
1092 | <span class="special">)</span> <span class="special">;</span></code> | |
1093 | </p></blockquote></div> | |
1094 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
1095 | <span class="bold"><strong>Effect:</strong></span> Same as <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> | |
1096 | <span class="keyword">const</span><span class="special">&</span> | |
1097 | <span class="identifier">rhs</span> <span class="special">)</span></code>. | |
1098 | </li></ul></div> | |
1099 | <p> | |
1100 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1101 | </p> | |
1102 | <a name="reference_optional_operator_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1103 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> | |
1104 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> | |
1105 | <span class="special">)</span> <span class="special">;</span></code> | |
1106 | </p></blockquote></div> | |
1107 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1108 | <li class="listitem"> | |
1109 | <p class="simpara"> | |
1110 | <span class="bold"><strong>Effect:</strong></span> | |
1111 | </p> | |
1112 | <div class="informaltable"><table class="table"> | |
1113 | <colgroup> | |
1114 | <col> | |
1115 | <col> | |
1116 | <col> | |
1117 | </colgroup> | |
1118 | <thead><tr></tr></thead> | |
1119 | <tbody> | |
1120 | <tr> | |
1121 | <td> | |
1122 | </td> | |
1123 | <td> | |
1124 | <p> | |
1125 | <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span> | |
1126 | </p> | |
1127 | </td> | |
1128 | <td> | |
1129 | <p> | |
1130 | <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span> | |
1131 | </p> | |
1132 | </td> | |
1133 | </tr> | |
1134 | <tr> | |
1135 | <td> | |
1136 | <p> | |
1137 | <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code> | |
1138 | contains a value</strong></span> | |
1139 | </p> | |
1140 | </td> | |
1141 | <td> | |
1142 | <p> | |
1143 | assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> | |
1144 | to the contained value | |
1145 | </p> | |
1146 | </td> | |
1147 | <td> | |
1148 | <p> | |
1149 | initializes the contained value as if direct-initializing | |
1150 | an object of type <code class="computeroutput"><span class="identifier">T</span></code> | |
1151 | with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> | |
1152 | </p> | |
1153 | </td> | |
1154 | </tr> | |
1155 | <tr> | |
1156 | <td> | |
1157 | <p> | |
1158 | <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code> | |
1159 | does not contain a value</strong></span> | |
1160 | </p> | |
1161 | </td> | |
1162 | <td> | |
1163 | <p> | |
1164 | destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code> | |
1165 | </p> | |
1166 | </td> | |
1167 | <td> | |
1168 | <p> | |
1169 | no effect | |
1170 | </p> | |
1171 | </td> | |
1172 | </tr> | |
1173 | </tbody> | |
1174 | </table></div> | |
1175 | </li> | |
1176 | <li class="listitem"> | |
1177 | <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>. | |
1178 | </li> | |
1179 | <li class="listitem"> | |
1180 | <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>. | |
1181 | </li> | |
1182 | <li class="listitem"> | |
1183 | <span class="bold"><strong>Exception Safety:</strong></span> If any exception | |
1184 | is thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception | |
1185 | is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s | |
1186 | constructor, no effect. If an exception is thrown during the call to | |
1187 | <code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the | |
1188 | state of its contained value is as defined by the exception safety | |
1189 | guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s copy | |
1190 | assignment. | |
1191 | </li> | |
1192 | <li class="listitem"> | |
1193 | <span class="bold"><strong>Example:</strong></span> | |
1194 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> | |
1195 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> | |
1196 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span> | |
1197 | ||
1198 | <span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">opt0</span> <span class="special">;</span> | |
1199 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
1200 | </pre> | |
1201 | </li> | |
1202 | </ul></div> | |
1203 | <p> | |
1204 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1205 | </p> | |
1206 | <a name="reference_optional_operator_move_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1207 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> | |
1208 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> <span class="identifier">rhs</span> | |
1209 | <span class="special">)</span> <span class="special">;</span></code> | |
1210 | </p></blockquote></div> | |
1211 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1212 | <li class="listitem"> | |
1213 | <p class="simpara"> | |
1214 | <span class="bold"><strong>Effect:</strong></span> | |
1215 | </p> | |
1216 | <div class="informaltable"><table class="table"> | |
1217 | <colgroup> | |
1218 | <col> | |
1219 | <col> | |
1220 | <col> | |
1221 | </colgroup> | |
1222 | <thead><tr></tr></thead> | |
1223 | <tbody> | |
1224 | <tr> | |
1225 | <td> | |
1226 | </td> | |
1227 | <td> | |
1228 | <p> | |
1229 | <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span> | |
1230 | </p> | |
1231 | </td> | |
1232 | <td> | |
1233 | <p> | |
1234 | <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span> | |
1235 | </p> | |
1236 | </td> | |
1237 | </tr> | |
1238 | <tr> | |
1239 | <td> | |
1240 | <p> | |
1241 | <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code> | |
1242 | contains a value</strong></span> | |
1243 | </p> | |
1244 | </td> | |
1245 | <td> | |
1246 | <p> | |
1247 | assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value | |
1248 | </p> | |
1249 | </td> | |
1250 | <td> | |
1251 | <p> | |
1252 | initializes the contained value as if direct-initializing | |
1253 | an object of type <code class="computeroutput"><span class="identifier">T</span></code> | |
1254 | with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> | |
1255 | </p> | |
1256 | </td> | |
1257 | </tr> | |
1258 | <tr> | |
1259 | <td> | |
1260 | <p> | |
1261 | <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code> | |
1262 | does not contain a value</strong></span> | |
1263 | </p> | |
1264 | </td> | |
1265 | <td> | |
1266 | <p> | |
1267 | destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code> | |
1268 | </p> | |
1269 | </td> | |
1270 | <td> | |
1271 | <p> | |
1272 | no effect | |
1273 | </p> | |
1274 | </td> | |
1275 | </tr> | |
1276 | </tbody> | |
1277 | </table></div> | |
1278 | </li> | |
1279 | <li class="listitem"> | |
1280 | <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>. | |
1281 | </li> | |
1282 | <li class="listitem"> | |
1283 | <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>. | |
1284 | </li> | |
1285 | <li class="listitem"> | |
1286 | <span class="bold"><strong>Exception Safety:</strong></span> If any exception | |
1287 | is thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception | |
1288 | is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s | |
1289 | constructor, no effect. If an exception is thrown during the call to | |
1290 | <code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the | |
1291 | state of its contained value is as defined by the exception safety | |
1292 | guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s copy | |
1293 | assignment. | |
1294 | </li> | |
1295 | <li class="listitem"> | |
1296 | <span class="bold"><strong>Example:</strong></span> | |
1297 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> | |
1298 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> | |
1299 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span> | |
1300 | ||
1301 | <span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">;</span> | |
1302 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span> | |
1303 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt1</span> <span class="special">)</span> | |
1304 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
1305 | </pre> | |
1306 | </li> | |
1307 | </ul></div> | |
1308 | <p> | |
1309 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1310 | </p> | |
1311 | <a name="reference_optional_emplace"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1312 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">></span> | |
1313 | <span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
1314 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">emplace</span><span class="special">(</span> | |
1315 | <span class="identifier">Args</span><span class="special">...&&</span> | |
1316 | <span class="identifier">args</span> <span class="special">);</span></code> | |
1317 | </p></blockquote></div> | |
1318 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1319 | <li class="listitem"> | |
1320 | <span class="bold"><strong>Requires:</strong></span> The compiler supports rvalue | |
1321 | references and variadic templates. | |
1322 | </li> | |
1323 | <li class="listitem"> | |
1324 | <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized calls <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">=</span> <span class="identifier">none</span></code>. | |
1325 | Then initializes in-place the contained value as if direct-initializing | |
1326 | an object of type <code class="computeroutput"><span class="identifier">T</span></code> | |
1327 | with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">Args</span><span class="special">>(</span><span class="identifier">args</span><span class="special">)...</span></code>. | |
1328 | </li> | |
1329 | <li class="listitem"> | |
1330 | <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>. | |
1331 | </li> | |
1332 | <li class="listitem"> | |
1333 | <span class="bold"><strong>Throws:</strong></span> Whatever the selected <code class="computeroutput"><span class="identifier">T</span></code>'s constructor throws. | |
1334 | </li> | |
1335 | <li class="listitem"> | |
1336 | <span class="bold"><strong>Exception Safety:</strong></span> If an exception | |
1337 | is thrown during the initialization of <code class="computeroutput"><span class="identifier">T</span></code>, | |
1338 | <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
1339 | is <span class="emphasis"><em>uninitialized</em></span>. | |
1340 | </li> | |
1341 | <li class="listitem"> | |
1342 | <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> | |
1343 | need not be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code> | |
1344 | or <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>. | |
1345 | On compilers that do not support variadic templates, the signature | |
1346 | falls back to two overloads:<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> | |
1347 | <span class="identifier">Arg</span><span class="special">></span> | |
1348 | <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="identifier">Arg</span><span class="special">&&</span> <span class="identifier">arg</span><span class="special">)</span></code> and <code class="computeroutput"><span class="keyword">void</span> | |
1349 | <span class="identifier">emplace</span><span class="special">()</span></code>. | |
1350 | On compilers that do not support rvalue references, the signature falls | |
1351 | back to three overloads: taking <code class="computeroutput"><span class="keyword">const</span></code> | |
1352 | and non-<code class="computeroutput"><span class="keyword">const</span></code> lvalue reference, | |
1353 | and third with empty function argument list. | |
1354 | </li> | |
1355 | <li class="listitem"> | |
1356 | <span class="bold"><strong>Example:</strong></span> | |
1357 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> | |
1358 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">;</span> | |
1359 | <span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">(</span><span class="number">0</span><span class="special">);</span> <span class="comment">// create in-place using ctor T(int)</span> | |
1360 | <span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">();</span> <span class="comment">// destroy previous and default-construct another T</span> | |
1361 | <span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> <span class="comment">// destroy and copy-construct in-place (no assignment called)</span> | |
1362 | </pre> | |
1363 | </li> | |
1364 | </ul></div> | |
1365 | <p> | |
1366 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1367 | </p> | |
1368 | <a name="reference_optional_operator_equal_factory"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1369 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span> | |
1370 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> | |
1371 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">InPlaceFactory</span> | |
1372 | <span class="keyword">const</span><span class="special">&</span> | |
1373 | <span class="identifier">f</span> <span class="special">);</span></code> | |
1374 | </p></blockquote></div> | |
1375 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1376 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span> | |
1377 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> | |
1378 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">TypedInPlaceFactory</span> | |
1379 | <span class="keyword">const</span><span class="special">&</span> | |
1380 | <span class="identifier">f</span> <span class="special">);</span></code> | |
1381 | </p></blockquote></div> | |
1382 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1383 | <li class="listitem"> | |
1384 | <span class="bold"><strong>Effect:</strong></span> Assigns an <code class="computeroutput"><span class="identifier">optional</span></code> | |
1385 | with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained | |
1386 | from the factory. | |
1387 | </li> | |
1388 | <li class="listitem"> | |
1389 | <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span> | |
1390 | and its value is <span class="emphasis"><em>directly given</em></span> from the factory | |
1391 | <code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value | |
1392 | <span class="underline">is not copied</span>). | |
1393 | </li> | |
1394 | <li class="listitem"> | |
1395 | <span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code> constructor called by the factory | |
1396 | throws. | |
1397 | </li> | |
1398 | <li class="listitem"> | |
1399 | <span class="bold"><strong>Notes:</strong></span> See <a class="link" href="../../tutorial/in_place_factories.html" title="In-Place Factories">In-Place | |
1400 | Factories</a> | |
1401 | </li> | |
1402 | <li class="listitem"> | |
1403 | <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only | |
1404 | be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code> | |
1405 | constructor used by the factory; in that case, the <code class="computeroutput"><span class="identifier">optional</span></code> | |
1406 | object will be reset to be <span class="emphasis"><em>uninitialized</em></span>. | |
1407 | </li> | |
1408 | </ul></div> | |
1409 | <p> | |
1410 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1411 | </p> | |
1412 | <a name="reference_optional_reset_value"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1413 | <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
1414 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">reset</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code> | |
1415 | </p></blockquote></div> | |
1416 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
1417 | <span class="bold"><strong>Deprecated:</strong></span> same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=</span> | |
1418 | <span class="special">(</span> <span class="identifier">T</span> | |
1419 | <span class="keyword">const</span><span class="special">&</span> | |
1420 | <span class="identifier">v</span><span class="special">)</span> | |
1421 | <span class="special">;</span></code> | |
1422 | </li></ul></div> | |
1423 | <p> | |
1424 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1425 | </p> | |
1426 | <a name="reference_optional_reset"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1427 | <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span> | |
1428 | <span class="special">;</span></code> | |
1429 | </p></blockquote></div> | |
1430 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
1431 | <span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=(</span> | |
1432 | <span class="identifier">none_t</span> <span class="special">);</span></code> | |
1433 | </li></ul></div> | |
1434 | <p> | |
1435 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1436 | </p> | |
1437 | <a name="reference_optional_get"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1438 | <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
1439 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code> | |
1440 | </p></blockquote></div> | |
1441 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1442 | <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> | |
1443 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="special">;</span></code> | |
1444 | </p></blockquote></div> | |
1445 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1446 | <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span> | |
1447 | <span class="keyword">const</span><span class="special">&</span> | |
1448 | <span class="identifier">get</span> <span class="special">(</span> | |
1449 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code> | |
1450 | </p></blockquote></div> | |
1451 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1452 | <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span> | |
1453 | <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
1454 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> | |
1455 | <span class="special">&)</span> <span class="special">;</span></code> | |
1456 | </p></blockquote></div> | |
1457 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1458 | <li class="listitem"> | |
1459 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized | |
1460 | </li> | |
1461 | <li class="listitem"> | |
1462 | <span class="bold"><strong>Returns:</strong></span> A reference to the contained | |
1463 | value | |
1464 | </li> | |
1465 | <li class="listitem"> | |
1466 | <span class="bold"><strong>Throws:</strong></span> Nothing. | |
1467 | </li> | |
1468 | <li class="listitem"> | |
1469 | <span class="bold"><strong>Notes:</strong></span> The requirement is asserted | |
1470 | via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. | |
1471 | </li> | |
1472 | </ul></div> | |
1473 | <p> | |
1474 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1475 | </p> | |
1476 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1477 | <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code> | |
1478 | </p></blockquote></div> | |
1479 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1480 | <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> | |
1481 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get</span><span class="special">()</span> <span class="special">;</span></code> | |
1482 | </p></blockquote></div> | |
1483 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1484 | <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span> | |
1485 | <span class="keyword">const</span><span class="special">&</span> | |
1486 | <span class="identifier">get</span> <span class="special">(</span> | |
1487 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> | |
1488 | <span class="keyword">const</span><span class="special">&</span> | |
1489 | <span class="special">)</span> <span class="special">;</span></code> | |
1490 | </p></blockquote></div> | |
1491 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1492 | <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span> | |
1493 | <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="special">&)</span> | |
1494 | <span class="special">;</span></code> | |
1495 | </p></blockquote></div> | |
1496 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1497 | <li class="listitem"> | |
1498 | <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized | |
1499 | </li> | |
1500 | <li class="listitem"> | |
1501 | <span class="bold"><strong>Returns:</strong></span> <span class="underline">The</span> | |
1502 | reference contained. | |
1503 | </li> | |
1504 | <li class="listitem"> | |
1505 | <span class="bold"><strong>Throws:</strong></span> Nothing. | |
1506 | </li> | |
1507 | <li class="listitem"> | |
1508 | <span class="bold"><strong>Notes:</strong></span> The requirement is asserted | |
1509 | via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. | |
1510 | </li> | |
1511 | </ul></div> | |
1512 | <p> | |
1513 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1514 | </p> | |
1515 | <a name="reference_optional_operator_asterisk"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1516 | <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
1517 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> | |
1518 | <span class="keyword">const</span><span class="special">&</span> | |
1519 | <span class="special">;</span></code> | |
1520 | </p></blockquote></div> | |
1521 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1522 | <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> | |
1523 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&;</span></code> | |
1524 | </p></blockquote></div> | |
1525 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1526 | <li class="listitem"> | |
1527 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized | |
1528 | </li> | |
1529 | <li class="listitem"> | |
1530 | <span class="bold"><strong>Returns:</strong></span> A reference to the contained | |
1531 | value | |
1532 | </li> | |
1533 | <li class="listitem"> | |
1534 | <span class="bold"><strong>Throws:</strong></span> Nothing. | |
1535 | </li> | |
1536 | <li class="listitem"> | |
1537 | <span class="bold"><strong>Notes:</strong></span> The requirement is asserted | |
1538 | via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. | |
1539 | On compilers that do not support ref-qualifiers on member functions | |
1540 | these two overloads are replaced with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code> and non-<code class="computeroutput"><span class="keyword">const</span></code> | |
1541 | member functions. | |
1542 | </li> | |
1543 | <li class="listitem"> | |
1544 | <span class="bold"><strong>Example:</strong></span> | |
1545 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span> | |
1546 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span> | |
1547 | <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span> | |
1548 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
1549 | <span class="identifier">T</span> <span class="identifier">w</span> <span class="special">;</span> | |
1550 | <span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">w</span> <span class="special">;</span> | |
1551 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">w</span> <span class="special">)</span> <span class="special">;</span> | |
1552 | </pre> | |
1553 | </li> | |
1554 | </ul></div> | |
1555 | <p> | |
1556 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1557 | </p> | |
1558 | <a name="reference_optional_operator_asterisk_move"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1559 | <code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span> | |
1560 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&&;</span></code> | |
1561 | </p></blockquote></div> | |
1562 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1563 | <li class="listitem"> | |
1564 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value. | |
1565 | </li> | |
1566 | <li class="listitem"> | |
1567 | <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">val</span><span class="special">);</span></code>. | |
1568 | </li> | |
1569 | <li class="listitem"> | |
1570 | <span class="bold"><strong>Notes:</strong></span> The requirement is asserted | |
1571 | via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. | |
1572 | On compilers that do not support ref-qualifiers on member functions | |
1573 | this overload is not present. | |
1574 | </li> | |
1575 | </ul></div> | |
1576 | <p> | |
1577 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1578 | </p> | |
1579 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1580 | <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span> | |
1581 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span> | |
1582 | <span class="keyword">const</span><span class="special">&</span> | |
1583 | <span class="special">;</span></code> | |
1584 | </p></blockquote></div> | |
1585 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1586 | <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span> | |
1587 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span> | |
1588 | <span class="special">&</span> <span class="special">;</span></code> | |
1589 | </p></blockquote></div> | |
1590 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1591 | <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span> | |
1592 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span> | |
1593 | <span class="special">&&</span> <span class="special">;</span></code> | |
1594 | </p></blockquote></div> | |
1595 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1596 | <li class="listitem"> | |
1597 | <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized | |
1598 | </li> | |
1599 | <li class="listitem"> | |
1600 | <span class="bold"><strong>Returns:</strong></span> <span class="underline">The</span> | |
1601 | reference contained. | |
1602 | </li> | |
1603 | <li class="listitem"> | |
1604 | <span class="bold"><strong>Throws:</strong></span> Nothing. | |
1605 | </li> | |
1606 | <li class="listitem"> | |
1607 | <span class="bold"><strong>Notes:</strong></span> The requirement is asserted | |
1608 | via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. | |
1609 | On compilers that do not support ref-qualifiers on member functions | |
1610 | these three overloads are replaced with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code> and non-<code class="computeroutput"><span class="keyword">const</span></code> | |
1611 | member functions. | |
1612 | </li> | |
1613 | <li class="listitem"> | |
1614 | <span class="bold"><strong>Example:</strong></span> | |
1615 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span> | |
1616 | <span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span> | |
1617 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">vref</span> <span class="special">);</span> | |
1618 | <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">vref2</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span> | |
1619 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">vref2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
1620 | <span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span> | |
1621 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
1622 | </pre> | |
1623 | </li> | |
1624 | </ul></div> | |
1625 | <p> | |
1626 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1627 | </p> | |
1628 | <a name="reference_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1629 | <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code> | |
1630 | </p></blockquote></div> | |
1631 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1632 | <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> | |
1633 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&</span> <span class="special">;</span></code> | |
1634 | </p></blockquote></div> | |
1635 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1636 | <li class="listitem"> | |
1637 | <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="special">*</span><span class="identifier">val</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>. | |
1638 | </li> | |
1639 | <li class="listitem"> | |
1640 | <span class="bold"><strong>Notes:</strong></span> On compilers that do not support | |
1641 | ref-qualifiers on member functions these two overloads are replaced | |
1642 | with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code> | |
1643 | and non-<code class="computeroutput"><span class="keyword">const</span></code> member functions. | |
1644 | </li> | |
1645 | <li class="listitem"> | |
1646 | <span class="bold"><strong>Example:</strong></span> | |
1647 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span> | |
1648 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o0</span><span class="special">,</span> <span class="identifier">o1</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span> | |
1649 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">);</span> | |
1650 | ||
1651 | <span class="keyword">try</span> <span class="special">{</span> | |
1652 | <span class="identifier">o0</span><span class="special">.</span><span class="identifier">value</span><span class="special">();</span> <span class="comment">// throws</span> | |
1653 | <span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">false</span> <span class="special">);</span> | |
1654 | <span class="special">}</span> | |
1655 | <span class="keyword">catch</span><span class="special">(</span><span class="identifier">bad_optional_access</span><span class="special">&)</span> <span class="special">{</span> | |
1656 | <span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">true</span> <span class="special">);</span> | |
1657 | <span class="special">}</span> | |
1658 | </pre> | |
1659 | </li> | |
1660 | </ul></div> | |
1661 | <p> | |
1662 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1663 | </p> | |
1664 | <a name="reference_optional_value_move"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1665 | <code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span> | |
1666 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&&</span> <span class="special">;</span></code> | |
1667 | </p></blockquote></div> | |
1668 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1669 | <li class="listitem"> | |
1670 | <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">val</span><span class="special">)</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>. | |
1671 | </li> | |
1672 | <li class="listitem"> | |
1673 | <span class="bold"><strong>Notes:</strong></span> On compilers that do not support | |
1674 | ref-qualifiers on member functions this overload is not present. | |
1675 | </li> | |
1676 | </ul></div> | |
1677 | <p> | |
1678 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1679 | </p> | |
1680 | <a name="reference_optional_value_or"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1681 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span> | |
1682 | <span class="identifier">v</span><span class="special">)</span> | |
1683 | <span class="keyword">const</span><span class="special">&</span> | |
1684 | <span class="special">;</span></code> | |
1685 | </p></blockquote></div> | |
1686 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1687 | <li class="listitem"> | |
1688 | <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span> | |
1689 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">);</span></code>. | |
1690 | </li> | |
1691 | <li class="listitem"> | |
1692 | <span class="bold"><strong>Remarks:</strong></span> If <code class="computeroutput"><span class="identifier">T</span></code> | |
1693 | is not <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> or <code class="computeroutput"><span class="identifier">U</span> <span class="special">&&</span></code> | |
1694 | is not convertible to <code class="computeroutput"><span class="identifier">T</span></code>, | |
1695 | the program is ill-formed. | |
1696 | </li> | |
1697 | <li class="listitem"> | |
1698 | <span class="bold"><strong>Notes:</strong></span> On compilers that do not support | |
1699 | ref-qualifiers on member functions this overload is replaced with the | |
1700 | <code class="computeroutput"><span class="keyword">const</span></code>-qualified member | |
1701 | function. On compilers without rvalue reference support the type of | |
1702 | <code class="computeroutput"><span class="identifier">v</span></code> becomes <code class="computeroutput"><span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span></code>. | |
1703 | </li> | |
1704 | </ul></div> | |
1705 | <p> | |
1706 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1707 | </p> | |
1708 | <a name="reference_optional_value_or_move"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1709 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span> | |
1710 | <span class="identifier">v</span><span class="special">)</span> | |
1711 | <span class="special">&&</span> <span class="special">;</span></code> | |
1712 | </p></blockquote></div> | |
1713 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1714 | <li class="listitem"> | |
1715 | <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">);</span></code>. | |
1716 | </li> | |
1717 | <li class="listitem"> | |
1718 | <span class="bold"><strong>Remarks:</strong></span> If <code class="computeroutput"><span class="identifier">T</span></code> | |
1719 | is not <code class="computeroutput"><span class="identifier">MoveConstructible</span></code> | |
1720 | or <code class="computeroutput"><span class="identifier">U</span> <span class="special">&&</span></code> | |
1721 | is not convertible to <code class="computeroutput"><span class="identifier">T</span></code>, | |
1722 | the program is ill-formed. | |
1723 | </li> | |
1724 | <li class="listitem"> | |
1725 | <span class="bold"><strong>Notes:</strong></span> On compilers that do not support | |
1726 | ref-qualifiers on member functions this overload is not present. | |
1727 | </li> | |
1728 | </ul></div> | |
1729 | <p> | |
1730 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1731 | </p> | |
1732 | <a name="reference_optional_value_or_call"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1733 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code> | |
1734 | </p></blockquote></div> | |
1735 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1736 | <li class="listitem"> | |
1737 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> | |
1738 | is <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> and <code class="computeroutput"><span class="identifier">F</span></code> models a <a href="http://www.sgi.com/tech/stl/Generator.html" target="_top"><code class="computeroutput"><span class="identifier">Generator</span></code></a> whose result type | |
1739 | is convertible to <code class="computeroutput"><span class="identifier">T</span></code>. | |
1740 | </li> | |
1741 | <li class="listitem"> | |
1742 | <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span> | |
1743 | <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">f</span><span class="special">();</span></code>. | |
1744 | </li> | |
1745 | <li class="listitem"> | |
1746 | <span class="bold"><strong>Notes:</strong></span> On compilers that do not support | |
1747 | ref-qualifiers on member functions this overload is replaced with the | |
1748 | <code class="computeroutput"><span class="keyword">const</span></code>-qualified member | |
1749 | function. | |
1750 | </li> | |
1751 | <li class="listitem"> | |
1752 | <span class="bold"><strong>Example:</strong></span> | |
1753 | <pre class="programlisting"><span class="keyword">int</span> <span class="identifier">complain_and_0</span><span class="special">()</span> | |
1754 | <span class="special">{</span> | |
1755 | <span class="identifier">clog</span> <span class="special"><<</span> <span class="string">"no value returned, using default"</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> | |
1756 | <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> | |
1757 | <span class="special">}</span> | |
1758 | ||
1759 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">o1</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span> | |
1760 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">oN</span> <span class="special">=</span> <span class="identifier">none</span><span class="special">;</span> | |
1761 | ||
1762 | <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">complain_and_0</span><span class="special">);</span> <span class="comment">// fun not called</span> | |
1763 | <span class="identifier">assert</span> <span class="special">(</span><span class="identifier">i</span> <span class="special">==</span> <span class="number">1</span><span class="special">);</span> | |
1764 | ||
1765 | <span class="keyword">int</span> <span class="identifier">j</span> <span class="special">=</span> <span class="identifier">oN</span><span class="special">.</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">complain_and_0</span><span class="special">);</span> <span class="comment">// fun called</span> | |
1766 | <span class="identifier">assert</span> <span class="special">(</span><span class="identifier">i</span> <span class="special">==</span> <span class="number">0</span><span class="special">);</span> | |
1767 | </pre> | |
1768 | </li> | |
1769 | </ul></div> | |
1770 | <p> | |
1771 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1772 | </p> | |
1773 | <a name="reference_optional_value_or_call_move"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1774 | <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="special">&&</span> | |
1775 | <span class="special">;</span></code> | |
1776 | </p></blockquote></div> | |
1777 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1778 | <li class="listitem"> | |
1779 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> | |
1780 | is <code class="computeroutput"><span class="identifier">MoveConstructible</span></code> | |
1781 | and <code class="computeroutput"><span class="identifier">F</span></code> models a <a href="http://www.sgi.com/tech/stl/Generator.html" target="_top"><code class="computeroutput"><span class="identifier">Generator</span></code></a> | |
1782 | whose result type is convertible to <code class="computeroutput"><span class="identifier">T</span></code>. | |
1783 | </li> | |
1784 | <li class="listitem"> | |
1785 | <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span> | |
1786 | <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span> | |
1787 | <span class="identifier">f</span><span class="special">();</span></code>. | |
1788 | </li> | |
1789 | <li class="listitem"> | |
1790 | <span class="bold"><strong>Notes:</strong></span> On compilers that do not support | |
1791 | ref-qualifiers on member functions this overload is not present. | |
1792 | </li> | |
1793 | </ul></div> | |
1794 | <p> | |
1795 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1796 | </p> | |
1797 | <a name="reference_optional_get_value_or_value"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1798 | <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
1799 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span> | |
1800 | <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span></code> | |
1801 | </p></blockquote></div> | |
1802 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1803 | <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span> | |
1804 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="keyword">default</span> | |
1805 | <span class="special">)</span> <span class="special">;</span></code> | |
1806 | </p></blockquote></div> | |
1807 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1808 | <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span> | |
1809 | <span class="keyword">const</span><span class="special">&</span> | |
1810 | <span class="identifier">get_optional_value_or</span> <span class="special">(</span> | |
1811 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">o</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span> <span class="special">)</span> <span class="special">;</span></code> | |
1812 | </p></blockquote></div> | |
1813 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1814 | <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get_optional_value_or</span> | |
1815 | <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
1816 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>&</span> | |
1817 | <span class="identifier">o</span><span class="special">,</span> | |
1818 | <span class="identifier">T</span><span class="special">&</span> | |
1819 | <span class="keyword">default</span> <span class="special">)</span> | |
1820 | <span class="special">;</span></code> | |
1821 | </p></blockquote></div> | |
1822 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1823 | <li class="listitem"> | |
1824 | <span class="bold"><strong>Deprecated:</strong></span> Use <code class="computeroutput"><span class="identifier">value_or</span><span class="special">()</span></code> instead. | |
1825 | </li> | |
1826 | <li class="listitem"> | |
1827 | <span class="bold"><strong>Returns:</strong></span> A reference to the contained | |
1828 | value, if any, or <code class="computeroutput"><span class="keyword">default</span></code>. | |
1829 | </li> | |
1830 | <li class="listitem"> | |
1831 | <span class="bold"><strong>Throws:</strong></span> Nothing. | |
1832 | </li> | |
1833 | <li class="listitem"> | |
1834 | <span class="bold"><strong>Example:</strong></span> | |
1835 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">,</span> <span class="identifier">z</span> <span class="special">;</span> | |
1836 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span><span class="special">;</span> | |
1837 | <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">=</span> <span class="identifier">def</span><span class="special">.</span><span class="identifier">get_value_or</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span> | |
1838 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">y</span> <span class="special">==</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span> | |
1839 | ||
1840 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span> | |
1841 | <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="identifier">get_optional_value_or</span><span class="special">(</span><span class="identifier">opt</span><span class="special">,</span><span class="identifier">z</span><span class="special">);</span> | |
1842 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
1843 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">!=</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span> | |
1844 | </pre> | |
1845 | </li> | |
1846 | </ul></div> | |
1847 | <p> | |
1848 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1849 | </p> | |
1850 | <a name="reference_optional_get_ptr"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1851 | <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
1852 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span> | |
1853 | <span class="keyword">const</span> <span class="special">;</span></code> | |
1854 | </p></blockquote></div> | |
1855 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1856 | <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span> | |
1857 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span></code> | |
1858 | </p></blockquote></div> | |
1859 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1860 | <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span> | |
1861 | <span class="keyword">const</span><span class="special">*</span> | |
1862 | <span class="identifier">get_pointer</span> <span class="special">(</span> | |
1863 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code> | |
1864 | </p></blockquote></div> | |
1865 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1866 | <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get_pointer</span> | |
1867 | <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
1868 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> | |
1869 | <span class="special">&)</span> <span class="special">;</span></code> | |
1870 | </p></blockquote></div> | |
1871 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1872 | <li class="listitem"> | |
1873 | <span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized, a pointer to the | |
1874 | contained value; else <code class="computeroutput"><span class="number">0</span></code> | |
1875 | (<span class="emphasis"><em>null</em></span>). | |
1876 | </li> | |
1877 | <li class="listitem"> | |
1878 | <span class="bold"><strong>Throws:</strong></span> Nothing. | |
1879 | </li> | |
1880 | <li class="listitem"> | |
1881 | <span class="bold"><strong>Notes:</strong></span> The contained value is permanently | |
1882 | stored within <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>, | |
1883 | so you should not hold nor delete this pointer | |
1884 | </li> | |
1885 | <li class="listitem"> | |
1886 | <span class="bold"><strong>Example:</strong></span> | |
1887 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span> | |
1888 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> | |
1889 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span> <span class="identifier">copt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> | |
1890 | <span class="identifier">T</span><span class="special">*</span> <span class="identifier">p</span> <span class="special">=</span> <span class="identifier">opt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span> | |
1891 | <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">cp</span> <span class="special">=</span> <span class="identifier">copt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">();</span> | |
1892 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">p</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">opt</span><span class="special">)</span> <span class="special">);</span> | |
1893 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">cp</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">copt</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
1894 | </pre> | |
1895 | </li> | |
1896 | </ul></div> | |
1897 | <p> | |
1898 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1899 | </p> | |
1900 | <a name="reference_optional_operator_arrow"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1901 | <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> | |
1902 | <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span> <span class="special">->()</span> | |
1903 | <span class="keyword">const</span> <span class="special">;</span></code> | |
1904 | </p></blockquote></div> | |
1905 | <div class="blockquote"><blockquote class="blockquote"><p> | |
1906 | <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span> | |
1907 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span> | |
1908 | <span class="special">->()</span> <span class="special">;</span></code> | |
1909 | </p></blockquote></div> | |
1910 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1911 | <li class="listitem"> | |
1912 | <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized. | |
1913 | </li> | |
1914 | <li class="listitem"> | |
1915 | <span class="bold"><strong>Returns:</strong></span> A pointer to the contained | |
1916 | value. | |
1917 | </li> | |
1918 | <li class="listitem"> | |
1919 | <span class="bold"><strong>Throws:</strong></span> Nothing. | |
1920 | </li> | |
1921 | <li class="listitem"> | |
1922 | <span class="bold"><strong>Notes:</strong></span> The requirement is asserted | |
1923 | via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>. | |
1924 | </li> | |
1925 | <li class="listitem"> | |
1926 | <span class="bold"><strong>Example:</strong></span> | |
1927 | <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">X</span> <span class="special">{</span> <span class="keyword">int</span> <span class="identifier">mdata</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span> | |
1928 | <span class="identifier">X</span> <span class="identifier">x</span> <span class="special">;</span> | |
1929 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">X</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span> | |
1930 | <span class="identifier">opt</span><span class="special">-></span><span class="identifier">mdata</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> | |
1931 | </pre> | |
1932 | </li> | |
1933 | </ul></div> | |
1934 | <p> | |
1935 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1936 | </p> | |
1937 | <a name="reference_optional_operator_bool"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1938 | <code class="computeroutput"><span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span> | |
1939 | <span class="keyword">bool</span><span class="special">()</span> | |
1940 | <span class="keyword">const</span> <span class="keyword">noexcept</span> | |
1941 | <span class="special">;</span></code> | |
1942 | </p></blockquote></div> | |
1943 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1944 | <li class="listitem"> | |
1945 | <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</span></code>. | |
1946 | </li> | |
1947 | <li class="listitem"> | |
1948 | <span class="bold"><strong>Notes:</strong></span> On compilers that do not support | |
1949 | explicit conversion operators this falls back to safe-bool idiom. | |
1950 | </li> | |
1951 | <li class="listitem"> | |
1952 | <span class="bold"><strong>Example:</strong></span> | |
1953 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span> | |
1954 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">==</span> <span class="number">0</span> <span class="special">);</span> | |
1955 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> | |
1956 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">);</span> | |
1957 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">!=</span> <span class="number">0</span> <span class="special">);</span> | |
1958 | </pre> | |
1959 | </li> | |
1960 | </ul></div> | |
1961 | <p> | |
1962 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1963 | </p> | |
1964 | <a name="reference_optional_operator_not"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1965 | <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">noexcept</span> | |
1966 | <span class="special">;</span></code> | |
1967 | </p></blockquote></div> | |
1968 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
1969 | <li class="listitem"> | |
1970 | <span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>; else <code class="computeroutput"><span class="keyword">false</span></code>. | |
1971 | </li> | |
1972 | <li class="listitem"> | |
1973 | <span class="bold"><strong>Notes:</strong></span> This operator is provided for | |
1974 | those compilers which can't use the <span class="emphasis"><em>unspecified-bool-type | |
1975 | operator</em></span> in certain boolean contexts. | |
1976 | </li> | |
1977 | <li class="listitem"> | |
1978 | <span class="bold"><strong>Example:</strong></span> | |
1979 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">;</span> | |
1980 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">opt</span> <span class="special">);</span> | |
1981 | <span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">some_T</span> <span class="special">;</span> | |
1982 | ||
1983 | <span class="comment">// Notice the "double-bang" idiom here.</span> | |
1984 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!!</span><span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> | |
1985 | </pre> | |
1986 | </li> | |
1987 | </ul></div> | |
1988 | <p> | |
1989 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
1990 | </p> | |
1991 | <a name="reference_optional_is_initialized"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
1992 | <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code> | |
1993 | </p></blockquote></div> | |
1994 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
1995 | <span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">explicit</span> <span class="keyword">operator</span> | |
1996 | <span class="keyword">bool</span> <span class="special">()</span> | |
1997 | <span class="special">;</span></code> | |
1998 | </li></ul></div> | |
1999 | <p> | |
2000 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2001 | </p> | |
2002 | <h6> | |
2003 | <a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.h1"></a> | |
2004 | <span class="phrase"><a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.free_functions"></a></span><a class="link" href="detailed_semantics.html#boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.free_functions">Free | |
2005 | functions</a> | |
2006 | </h6> | |
2007 | <p> | |
2008 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2009 | </p> | |
2010 | <a name="reference_make_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2011 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code> | |
2012 | </p></blockquote></div> | |
2013 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
2014 | <li class="listitem"> | |
2015 | <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span> | |
2016 | type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>. | |
2017 | </li> | |
2018 | <li class="listitem"> | |
2019 | <span class="bold"><strong>Example:</strong></span> | |
2020 | <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span> | |
2021 | ||
2022 | <span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="number">1</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Creates an optional<int></span> | |
2023 | </pre> | |
2024 | </li> | |
2025 | </ul></div> | |
2026 | <p> | |
2027 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2028 | </p> | |
2029 | <a name="reference_make_optional_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2030 | <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> | |
2031 | <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code> | |
2032 | </p></blockquote></div> | |
2033 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
2034 | <li class="listitem"> | |
2035 | <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">condition</span><span class="special">,</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span> | |
2036 | type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>. | |
2037 | </li> | |
2038 | <li class="listitem"> | |
2039 | <span class="bold"><strong>Example:</strong></span> | |
2040 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">calculate_foo</span><span class="special">()</span> | |
2041 | <span class="special">{</span> | |
2042 | <span class="keyword">double</span> <span class="identifier">val</span> <span class="special">=</span> <span class="identifier">compute_foo</span><span class="special">();</span> | |
2043 | <span class="keyword">return</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="identifier">is_not_nan_and_finite</span><span class="special">(</span><span class="identifier">val</span><span class="special">),</span><span class="identifier">val</span><span class="special">);</span> | |
2044 | <span class="special">}</span> | |
2045 | ||
2046 | <span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">v</span> <span class="special">=</span> <span class="identifier">calculate_foo</span><span class="special">();</span> | |
2047 | <span class="keyword">if</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">v</span> <span class="special">)</span> | |
2048 | <span class="identifier">error</span><span class="special">(</span><span class="string">"foo wasn't computed"</span><span class="special">);</span> | |
2049 | </pre> | |
2050 | </li> | |
2051 | </ul></div> | |
2052 | <p> | |
2053 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2054 | </p> | |
2055 | <a name="reference_operator_compare_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2056 | <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> | |
2057 | <span class="special">==</span> <span class="special">(</span> | |
2058 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> | |
2059 | </p></blockquote></div> | |
2060 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
2061 | <li class="listitem"> | |
2062 | <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> | |
2063 | shall meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>. | |
2064 | </li> | |
2065 | <li class="listitem"> | |
2066 | <span class="bold"><strong>Returns:</strong></span> If both <code class="computeroutput"><span class="identifier">x</span></code> | |
2067 | and <code class="computeroutput"><span class="identifier">y</span></code> are initialized, | |
2068 | <code class="computeroutput"><span class="special">(*</span><span class="identifier">x</span> | |
2069 | <span class="special">==</span> <span class="special">*</span><span class="identifier">y</span><span class="special">)</span></code>. | |
2070 | If only <code class="computeroutput"><span class="identifier">x</span></code> or <code class="computeroutput"><span class="identifier">y</span></code> is initialized, <code class="computeroutput"><span class="keyword">false</span></code>. | |
2071 | If both are uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>. | |
2072 | </li> | |
2073 | <li class="listitem"> | |
2074 | <span class="bold"><strong>Notes:</strong></span> This definition guarantees | |
2075 | that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> | |
2076 | not containing a value is compared unequal to any <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> containing any value, and equal | |
2077 | to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> not containing a value. Pointers | |
2078 | have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code> | |
2079 | has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special">==</span></code> directly in generic code which expect | |
2080 | to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#equal" target="_top"><code class="computeroutput"><span class="identifier">equal_pointees</span><span class="special">()</span></code></a> | |
2081 | instead | |
2082 | </li> | |
2083 | <li class="listitem"> | |
2084 | <span class="bold"><strong>Example:</strong></span> | |
2085 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span> | |
2086 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">)),</span> <span class="identifier">o1_</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span> | |
2087 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o2</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">));</span> | |
2088 | ||
2089 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN</span> <span class="special">);</span> <span class="comment">// Identity implies equality</span> | |
2090 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1</span> <span class="special">);</span> <span class="comment">//</span> | |
2091 | ||
2092 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN_</span> <span class="special">);</span> <span class="comment">// Both uninitialized compare equal</span> | |
2093 | ||
2094 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">!=</span> <span class="identifier">o1</span> <span class="special">);</span> <span class="comment">// Initialized unequal to initialized.</span> | |
2095 | ||
2096 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1_</span> <span class="special">);</span> <span class="comment">// Both initialized compare as (*lhs == *rhs)</span> | |
2097 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">!=</span> <span class="identifier">o2</span> <span class="special">);</span> <span class="comment">//</span> | |
2098 | </pre> | |
2099 | </li> | |
2100 | </ul></div> | |
2101 | <p> | |
2102 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2103 | </p> | |
2104 | <a name="reference_operator_compare_less_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2105 | <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> | |
2106 | <span class="special"><</span> <span class="special">(</span> | |
2107 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> | |
2108 | </p></blockquote></div> | |
2109 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
2110 | <li class="listitem"> | |
2111 | <span class="bold"><strong>Requires:</strong></span> Expression <code class="computeroutput"><span class="special">*</span><span class="identifier">x</span> <span class="special"><</span> <span class="special">*</span><span class="identifier">y</span></code> shall be well-formed and its result | |
2112 | shall be convertible to <code class="computeroutput"><span class="keyword">bool</span></code>. | |
2113 | </li> | |
2114 | <li class="listitem"> | |
2115 | <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">(!</span><span class="identifier">y</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">false</span> <span class="special">:</span> <span class="special">(!</span><span class="identifier">x</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">true</span> <span class="special">:</span> <span class="special">*</span><span class="identifier">x</span> <span class="special"><</span> | |
2116 | <span class="special">*</span><span class="identifier">y</span></code>. | |
2117 | </li> | |
2118 | <li class="listitem"> | |
2119 | <span class="bold"><strong>Notes:</strong></span> This definition guarantees | |
2120 | that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> | |
2121 | not containing a value is ordered as less than any <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> containing any value, and equivalent | |
2122 | to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> not containing a value. Pointers | |
2123 | have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code> | |
2124 | has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code> directly in generic code which | |
2125 | expect to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#less" target="_top"><code class="computeroutput"><span class="identifier">less_pointees</span><span class="special">()</span></code></a> | |
2126 | instead. <code class="computeroutput"><span class="identifier">T</span></code> need not | |
2127 | be <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>. Only | |
2128 | single <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code> | |
2129 | is required. Other relational operations are defined in terms of this | |
2130 | one. If <code class="computeroutput"><span class="identifier">T</span></code>'s <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code> | |
2131 | satisfies the axioms of <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a> (transitivity, | |
2132 | antisymmetry and irreflexivity), <code class="computeroutput"><span class="identifier">optinal</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>. | |
2133 | </li> | |
2134 | <li class="listitem"> | |
2135 | <span class="bold"><strong>Example:</strong></span> | |
2136 | <pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span> | |
2137 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o0</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">0</span><span class="special">));</span> | |
2138 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span> | |
2139 | ||
2140 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Identity implies equivalence</span> | |
2141 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o1</span> <span class="special"><</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">);</span> | |
2142 | ||
2143 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">oN_</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Two uninitialized are equivalent</span> | |
2144 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN_</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span> | |
2145 | ||
2146 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">o0</span> <span class="special">);</span> <span class="comment">// Uninitialized is less than initialized</span> | |
2147 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o0</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span> | |
2148 | ||
2149 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special"><</span> <span class="identifier">o2</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Two initialized compare as (*lhs < *rhs)</span> | |
2150 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special"><</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
2151 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special"><</span> <span class="identifier">o2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> | |
2152 | </pre> | |
2153 | </li> | |
2154 | </ul></div> | |
2155 | <p> | |
2156 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2157 | </p> | |
2158 | <a name="reference_operator_compare_not_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2159 | <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> | |
2160 | <span class="special">!=</span> <span class="special">(</span> | |
2161 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> | |
2162 | </p></blockquote></div> | |
2163 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
2164 | <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span> | |
2165 | <span class="identifier">x</span> <span class="special">==</span> | |
2166 | <span class="identifier">y</span> <span class="special">);</span></code> | |
2167 | </li></ul></div> | |
2168 | <p> | |
2169 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2170 | </p> | |
2171 | <a name="reference_operator_compare_greater_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2172 | <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> | |
2173 | <span class="special">></span> <span class="special">(</span> | |
2174 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> | |
2175 | </p></blockquote></div> | |
2176 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
2177 | <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">(</span> | |
2178 | <span class="identifier">y</span> <span class="special"><</span> | |
2179 | <span class="identifier">x</span> <span class="special">);</span></code> | |
2180 | </li></ul></div> | |
2181 | <p> | |
2182 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2183 | </p> | |
2184 | <a name="reference_operator_compare_less_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2185 | <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> | |
2186 | <span class="special"><=</span> <span class="special">(</span> | |
2187 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> | |
2188 | </p></blockquote></div> | |
2189 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
2190 | <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span> | |
2191 | <span class="identifier">y</span> <span class="special"><</span> | |
2192 | <span class="identifier">x</span> <span class="special">);</span></code> | |
2193 | </li></ul></div> | |
2194 | <p> | |
2195 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2196 | </p> | |
2197 | <a name="reference_operator_compare_greater_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2198 | <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> | |
2199 | <span class="special">>=</span> <span class="special">(</span> | |
2200 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code> | |
2201 | </p></blockquote></div> | |
2202 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
2203 | <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span> | |
2204 | <span class="identifier">x</span> <span class="special"><</span> | |
2205 | <span class="identifier">y</span> <span class="special">);</span></code> | |
2206 | </li></ul></div> | |
2207 | <p> | |
2208 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2209 | </p> | |
2210 | <a name="reference_operator_compare_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2211 | <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> | |
2212 | <span class="special">==</span> <span class="special">(</span> | |
2213 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span> | |
2214 | <span class="keyword">noexcept</span><span class="special">;</span></code> | |
2215 | </p></blockquote></div> | |
2216 | <div class="blockquote"><blockquote class="blockquote"><p> | |
2217 | <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> | |
2218 | <span class="special">==</span> <span class="special">(</span> | |
2219 | <span class="identifier">none_t</span><span class="special">,</span> | |
2220 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code> | |
2221 | </p></blockquote></div> | |
2222 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
2223 | <li class="listitem"> | |
2224 | <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">!</span><span class="identifier">x</span></code>. | |
2225 | </li> | |
2226 | <li class="listitem"> | |
2227 | <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code> | |
2228 | need not meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>. | |
2229 | </li> | |
2230 | </ul></div> | |
2231 | <p> | |
2232 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2233 | </p> | |
2234 | <a name="reference_operator_compare_not_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2235 | <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> | |
2236 | <span class="special">!=</span> <span class="special">(</span> | |
2237 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span> | |
2238 | <span class="keyword">noexcept</span><span class="special">;</span></code> | |
2239 | </p></blockquote></div> | |
2240 | <div class="blockquote"><blockquote class="blockquote"><p> | |
2241 | <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span> | |
2242 | <span class="special">!=</span> <span class="special">(</span> | |
2243 | <span class="identifier">none_t</span><span class="special">,</span> | |
2244 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code> | |
2245 | </p></blockquote></div> | |
2246 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> | |
2247 | <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span> | |
2248 | <span class="identifier">x</span> <span class="special">==</span> | |
2249 | <span class="identifier">y</span> <span class="special">);</span></code> | |
2250 | </li></ul></div> | |
2251 | <p> | |
2252 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2253 | </p> | |
2254 | <a name="reference_swap_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2255 | <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span> | |
2256 | <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">y</span> | |
2257 | <span class="special">)</span> <span class="special">;</span></code> | |
2258 | </p></blockquote></div> | |
2259 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
2260 | <li class="listitem"> | |
2261 | <span class="bold"><strong>Requires:</strong></span> Lvalues of type <code class="computeroutput"><span class="identifier">T</span></code> shall be swappable and <code class="computeroutput"><span class="identifier">T</span></code> shall be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>. | |
2262 | </li> | |
2263 | <li class="listitem"> | |
2264 | <p class="simpara"> | |
2265 | <span class="bold"><strong>Effects:</strong></span> | |
2266 | </p> | |
2267 | <div class="informaltable"><table class="table"> | |
2268 | <colgroup> | |
2269 | <col> | |
2270 | <col> | |
2271 | <col> | |
2272 | </colgroup> | |
2273 | <thead><tr></tr></thead> | |
2274 | <tbody> | |
2275 | <tr> | |
2276 | <td> | |
2277 | </td> | |
2278 | <td> | |
2279 | <p> | |
2280 | <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span> | |
2281 | </p> | |
2282 | </td> | |
2283 | <td> | |
2284 | <p> | |
2285 | <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span> | |
2286 | </p> | |
2287 | </td> | |
2288 | </tr> | |
2289 | <tr> | |
2290 | <td> | |
2291 | <p> | |
2292 | <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code> | |
2293 | contains a value</strong></span> | |
2294 | </p> | |
2295 | </td> | |
2296 | <td> | |
2297 | <p> | |
2298 | calls <code class="computeroutput"><span class="identifier">swap</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">),</span> <span class="special">*</span><span class="identifier">rhs</span><span class="special">)</span></code> | |
2299 | </p> | |
2300 | </td> | |
2301 | <td> | |
2302 | <p> | |
2303 | initializes the contained value of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> as if direct-initializing | |
2304 | an object of type <code class="computeroutput"><span class="identifier">T</span></code> | |
2305 | with the expression <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>, followed by <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, | |
2306 | <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> | |
2307 | contains a value and <code class="computeroutput"><span class="identifier">rhs</span></code> | |
2308 | does not contain a value | |
2309 | </p> | |
2310 | </td> | |
2311 | </tr> | |
2312 | <tr> | |
2313 | <td> | |
2314 | <p> | |
2315 | <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code> | |
2316 | does not contain a value</strong></span> | |
2317 | </p> | |
2318 | </td> | |
2319 | <td> | |
2320 | <p> | |
2321 | initializes the contained value of <code class="computeroutput"><span class="identifier">rhs</span></code> | |
2322 | as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code> with the expression | |
2323 | <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">))</span></code>, | |
2324 | followed by <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value | |
2325 | and <code class="computeroutput"><span class="identifier">rhs</span></code> contains | |
2326 | a value | |
2327 | </p> | |
2328 | </td> | |
2329 | <td> | |
2330 | <p> | |
2331 | no effect | |
2332 | </p> | |
2333 | </td> | |
2334 | </tr> | |
2335 | </tbody> | |
2336 | </table></div> | |
2337 | </li> | |
2338 | <li class="listitem"> | |
2339 | <span class="bold"><strong>Postconditions:</strong></span> The states of <code class="computeroutput"><span class="identifier">x</span></code> and <code class="computeroutput"><span class="identifier">y</span></code> | |
2340 | interchanged. | |
2341 | </li> | |
2342 | <li class="listitem"> | |
2343 | <span class="bold"><strong>Throws:</strong></span> If both are initialized, whatever | |
2344 | <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code> | |
2345 | throws. If only one is initialized, whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code> | |
2346 | throws. | |
2347 | </li> | |
2348 | <li class="listitem"> | |
2349 | <span class="bold"><strong>Example:</strong></span> | |
2350 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span> | |
2351 | <span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span> | |
2352 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def0</span> <span class="special">;</span> | |
2353 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def1</span> <span class="special">;</span> | |
2354 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optX</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span> | |
2355 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optY</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span> | |
2356 | ||
2357 | <span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">def1</span><span class="special">);</span> <span class="comment">// no-op</span> | |
2358 | ||
2359 | <span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span> | |
2360 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span> | |
2361 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span> | |
2362 | ||
2363 | <span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span> <span class="comment">// Get back to original values</span> | |
2364 | ||
2365 | <span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span><span class="identifier">optY</span><span class="special">);</span> | |
2366 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">);</span> | |
2367 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optY</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span> | |
2368 | </pre> | |
2369 | </li> | |
2370 | </ul></div> | |
2371 | <p> | |
2372 | <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> | |
2373 | </p> | |
2374 | <a name="reference_swap_optional_reference"></a><div class="blockquote"><blockquote class="blockquote"><p> | |
2375 | <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span> | |
2376 | <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> <span class="identifier">y</span> | |
2377 | <span class="special">)</span> <span class="keyword">noexcept</span> | |
2378 | <span class="special">;</span></code> | |
2379 | </p></blockquote></div> | |
2380 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
2381 | <li class="listitem"> | |
2382 | <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="identifier">x</span></code> | |
2383 | refers to what <code class="computeroutput"><span class="identifier">y</span></code> refererred | |
2384 | to before the swap (if anything). <code class="computeroutput"><span class="identifier">y</span></code> | |
2385 | refers to whatever <code class="computeroutput"><span class="identifier">x</span></code> | |
2386 | referred to before the swap. | |
2387 | </li> | |
2388 | <li class="listitem"> | |
2389 | <span class="bold"><strong>Example:</strong></span> | |
2390 | <pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span> | |
2391 | <span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span> | |
2392 | ||
2393 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt0</span><span class="special">;</span> | |
2394 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">optX</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span> | |
2395 | <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">optY</span> <span class="special">(</span><span class="identifier">y</span><span class="special">);</span> | |
2396 | ||
2397 | <span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span> <span class="identifier">optY</span><span class="special">);</span> | |
2398 | <span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optX</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span> | |
2399 | <span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optY</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">x</span><span class="special">));</span> | |
2400 | ||
2401 | <span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">,</span> <span class="identifier">optX</span><span class="special">);</span> | |
2402 | <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span> | |
2403 | <span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span> | |
2404 | <span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span> | |
2405 | </pre> | |
2406 | [endsect] | |
2407 | </li> | |
2408 | </ul></div> | |
2409 | </div> | |
2410 | <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> | |
2411 | <td align="left"></td> | |
2412 | <td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2016 Andrzej Krzemieński<p> | |
2413 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
2414 | file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) | |
2415 | </p> | |
2416 | </div></td> | |
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