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24 | </div> | |
25 | <div class="section boost_bimap_the_tutorial_useful_functions"> | |
26 | <div class="titlepage"><div><div><h3 class="title"> | |
27 | <a name="boost_bimap.the_tutorial.useful_functions"></a><a class="link" href="useful_functions.html" title="Useful functions">Useful functions</a> | |
28 | </h3></div></div></div> | |
29 | <div class="toc"><dl> | |
30 | <dt><span class="section"><a href="useful_functions.html#boost_bimap.the_tutorial.useful_functions.projection_of_iterators">Projection | |
31 | of iterators</a></span></dt> | |
32 | <dt><span class="section"><a href="useful_functions.html#boost_bimap.the_tutorial.useful_functions.replace_and_modify">replace | |
33 | and modify</a></span></dt> | |
34 | <dt><span class="section"><a href="useful_functions.html#boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges">Retrieval | |
35 | of ranges</a></span></dt> | |
36 | </dl></div> | |
37 | <div class="section boost_bimap_the_tutorial_useful_functions_projection_of_iterators"> | |
38 | <div class="titlepage"><div><div><h4 class="title"> | |
39 | <a name="boost_bimap.the_tutorial.useful_functions.projection_of_iterators"></a><a class="link" href="useful_functions.html#boost_bimap.the_tutorial.useful_functions.projection_of_iterators" title="Projection of iterators">Projection | |
40 | of iterators</a> | |
41 | </h4></div></div></div> | |
42 | <p> | |
43 | Iterators can be projected to any of the three views of the bimap. A bimap | |
44 | provides three member functions to cope with projection: <code class="computeroutput"><span class="identifier">project_left</span></code>, <code class="computeroutput"><span class="identifier">project_right</span></code> | |
45 | and <code class="computeroutput"><span class="identifier">project_up</span></code>, with projects | |
46 | iterators to the <span class="emphasis"><em>left map view</em></span>, the <span class="emphasis"><em>right | |
47 | map view</em></span> and the <span class="emphasis"><em>collection of relations view</em></span>. | |
48 | These functions take any iterator from the bimap and retrieve an iterator | |
49 | over the projected view pointing to the same element. | |
50 | </p> | |
51 | <p> | |
52 | Here is an example that uses projection: | |
53 | </p> | |
54 | <p> | |
55 | <a href="../../../../example/projection.cpp" target="_top">Go to source code</a> | |
56 | </p> | |
57 | <p> | |
58 | </p> | |
59 | <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">bimap</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="identifier">multiset_of</span><span class="special"><</span><span class="keyword">int</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">greater</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="special">></span> <span class="special">></span> <span class="identifier">bm_type</span><span class="special">;</span> | |
60 | ||
61 | <span class="identifier">bm_type</span> <span class="identifier">bm</span><span class="special">;</span> | |
62 | <span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span><span class="string">"John"</span> <span class="special">,</span><span class="number">34</span><span class="special">)</span> <span class="special">);</span> | |
63 | <span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span><span class="string">"Peter"</span><span class="special">,</span><span class="number">24</span><span class="special">)</span> <span class="special">);</span> | |
64 | <span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span><span class="string">"Mary"</span> <span class="special">,</span><span class="number">12</span><span class="special">)</span> <span class="special">);</span> | |
65 | ||
66 | <span class="comment">// Find the name of the next younger person after Peter</span> | |
67 | ||
68 | <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_const_iterator</span> <span class="identifier">name_iter</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="string">"Peter"</span><span class="special">);</span> | |
69 | ||
70 | <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">right_const_iterator</span> <span class="identifier">years_iter</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">project_right</span><span class="special">(</span><span class="identifier">name_iter</span><span class="special">);</span> | |
71 | ||
72 | <span class="special">++</span><span class="identifier">years_iter</span><span class="special">;</span> | |
73 | ||
74 | <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"The next younger person after Peter is "</span> <span class="special"><<</span> <span class="identifier">years_iter</span><span class="special">-></span><span class="identifier">second</span><span class="special">;</span> | |
75 | </pre> | |
76 | <p> | |
77 | </p> | |
78 | </div> | |
79 | <div class="section boost_bimap_the_tutorial_useful_functions_replace_and_modify"> | |
80 | <div class="titlepage"><div><div><h4 class="title"> | |
81 | <a name="boost_bimap.the_tutorial.useful_functions.replace_and_modify"></a><a class="link" href="useful_functions.html#boost_bimap.the_tutorial.useful_functions.replace_and_modify" title="replace and modify">replace | |
82 | and modify</a> | |
83 | </h4></div></div></div> | |
84 | <p> | |
85 | These functions are members of the views of a bimap that are not founded | |
86 | in their standard counterparts. | |
87 | </p> | |
88 | <p> | |
89 | The <code class="computeroutput"><span class="identifier">replace</span></code> family member | |
90 | functions performs in-place replacement of a given element as the following | |
91 | example shows: | |
92 | </p> | |
93 | <p> | |
94 | <a href="../../../../example/tutorial_modify_and_replace.cpp" target="_top">Go to source | |
95 | code</a> | |
96 | </p> | |
97 | <p> | |
98 | </p> | |
99 | <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">bimap</span><span class="special"><</span> <span class="keyword">int</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="identifier">bm_type</span><span class="special">;</span> | |
100 | <span class="identifier">bm_type</span> <span class="identifier">bm</span><span class="special">;</span> | |
101 | ||
102 | <span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="string">"one"</span><span class="special">)</span> <span class="special">);</span> | |
103 | ||
104 | <span class="comment">// Replace (1,"one") with (1,"1") using the right map view</span> | |
105 | <span class="special">{</span> | |
106 | <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">right_iterator</span> <span class="identifier">it</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="string">"one"</span><span class="special">);</span> | |
107 | ||
108 | <span class="keyword">bool</span> <span class="identifier">successful_replace</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span><span class="special">.</span><span class="identifier">replace_key</span><span class="special">(</span> <span class="identifier">it</span><span class="special">,</span> <span class="string">"1"</span> <span class="special">);</span> | |
109 | ||
110 | <span class="identifier">assert</span><span class="special">(</span> <span class="identifier">successful_replace</span> <span class="special">);</span> | |
111 | <span class="special">}</span> | |
112 | ||
113 | <span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span><span class="number">2</span><span class="special">,</span><span class="string">"two"</span><span class="special">)</span> <span class="special">);</span> | |
114 | ||
115 | <span class="comment">// Fail to replace (1,"1") with (1,"two") using the left map view</span> | |
116 | <span class="special">{</span> | |
117 | <span class="identifier">assert</span><span class="special">(</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="number">2</span> <span class="special">);</span> | |
118 | ||
119 | <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_iterator</span> <span class="identifier">it</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> | |
120 | ||
121 | <span class="keyword">bool</span> <span class="identifier">successful_replace</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">replace_data</span><span class="special">(</span> <span class="identifier">it</span><span class="special">,</span> <span class="string">"two"</span> <span class="special">);</span> | |
122 | ||
123 | <a class="co" name="boost_bimap.the_tutorial.useful_functions.replace_and_modify.c0" href="useful_functions.html#boost_bimap.the_tutorial.useful_functions.replace_and_modify.c1"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a><span class="identifier">assert</span><span class="special">(</span> <span class="special">!</span> <span class="identifier">successful_replace</span> <span class="special">);</span> | |
124 | <span class="identifier">assert</span><span class="special">(</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="number">2</span> <span class="special">);</span> | |
125 | <span class="special">}</span> | |
126 | </pre> | |
127 | <p> | |
128 | </p> | |
129 | <div class="calloutlist"><table border="0" summary="Callout list"><tr> | |
130 | <td width="5%" valign="top" align="left"><p><a name="boost_bimap.the_tutorial.useful_functions.replace_and_modify.c1"></a><a href="#boost_bimap.the_tutorial.useful_functions.replace_and_modify.c0"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td> | |
131 | <td valign="top" align="left"><p> | |
132 | <code class="computeroutput"><span class="identifier">it</span></code> is still valid here, | |
133 | and the bimap was left unchanged | |
134 | </p></td> | |
135 | </tr></table></div> | |
136 | <p> | |
137 | <code class="computeroutput"><span class="identifier">replace</span></code> functions performs | |
138 | this substitution in such a manner that: | |
139 | </p> | |
140 | <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> | |
141 | <li class="listitem"> | |
142 | The complexity is constant time if the changed element retains its | |
143 | original order with respect to all views; it is logarithmic otherwise. | |
144 | </li> | |
145 | <li class="listitem"> | |
146 | Iterator and reference validity are preserved. | |
147 | </li> | |
148 | <li class="listitem"> | |
149 | The operation is strongly exception-safe, i.e. the <code class="computeroutput"><span class="identifier">bimap</span></code> | |
150 | remains unchanged if some exception (originated by the system or the | |
151 | user's data types) is thrown. | |
152 | </li> | |
153 | </ul></div> | |
154 | <p> | |
155 | <code class="computeroutput"><span class="identifier">replace</span></code> functions are powerful | |
156 | operations not provided by standard STL containers, and one that is specially | |
157 | handy when strong exception-safety is required. | |
158 | </p> | |
159 | <p> | |
160 | The observant reader might have noticed that the convenience of replace | |
161 | comes at a cost: namely the whole element has to be copied <span class="emphasis"><em>twice</em></span> | |
162 | to do the updating (when retrieving it and inside <code class="computeroutput"><span class="identifier">replace</span></code>). | |
163 | If elements are expensive to copy, this may be quite a computational cost | |
164 | for the modification of just a tiny part of the object. To cope with this | |
165 | situation, Boost.Bimap provides an alternative updating mechanism: <code class="computeroutput"><span class="identifier">modify</span></code> functions. | |
166 | </p> | |
167 | <p> | |
168 | <code class="computeroutput"><span class="identifier">modify</span></code> functions accepts | |
169 | a functor (or pointer to function) taking a reference to the data to be | |
170 | changed, thus eliminating the need for spurious copies. Like <code class="computeroutput"><span class="identifier">replace</span></code> functions, <code class="computeroutput"><span class="identifier">modify</span></code> | |
171 | functions does preserve the internal orderings of all the indices of the | |
172 | <code class="computeroutput"><span class="identifier">bimap</span></code>. However, the semantics | |
173 | of modify functions are not entirely equivalent to replace functions. Consider | |
174 | what happens if a collision occurs as a result of modifying the element, | |
175 | i.e. the modified element clashes with another with respect to some unique | |
176 | view. In the case of <code class="computeroutput"><span class="identifier">replace</span></code> | |
177 | functions, the original value is kept and the method returns without altering | |
178 | the container, but <code class="computeroutput"><span class="identifier">modify</span></code> | |
179 | functions cannot afford such an approach, since the modifying functor leaves | |
180 | no trace of the previous value of the element. Integrity constraints thus | |
181 | lead to the following policy: when a collision happens in the process of | |
182 | calling a modify functions, the element is erased and the method returns | |
183 | false. This difference in behavior between <code class="computeroutput"><span class="identifier">replace</span></code> | |
184 | and <code class="computeroutput"><span class="identifier">modify</span></code> functions has | |
185 | to be considered by the programmer on a case-by-case basis. | |
186 | </p> | |
187 | <p> | |
188 | Boost.Bimap defines new placeholders named <code class="computeroutput"><span class="identifier">_key</span></code> | |
189 | and <code class="computeroutput"><span class="identifier">_data</span></code> to allow a sounder | |
190 | solution. You have to include <code class="computeroutput"><span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">bimap</span><span class="special">/</span><span class="identifier">support</span><span class="special">/</span><span class="identifier">lambda</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> | |
191 | to use them. | |
192 | </p> | |
193 | <p> | |
194 | <a href="../../../../example/tutorial_modify_and_replace.cpp" target="_top">Go to source | |
195 | code</a> | |
196 | </p> | |
197 | <p> | |
198 | </p> | |
199 | <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">bimap</span><span class="special"><</span> <span class="keyword">int</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="identifier">bm_type</span><span class="special">;</span> | |
200 | <span class="identifier">bm_type</span> <span class="identifier">bm</span><span class="special">;</span> | |
201 | <span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="string">"one"</span><span class="special">)</span> <span class="special">);</span> | |
202 | ||
203 | <span class="comment">// Modify (1,"one") to (1,"1") using the right map view</span> | |
204 | <span class="special">{</span> | |
205 | <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">right_iterator</span> <span class="identifier">it</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="string">"one"</span><span class="special">);</span> | |
206 | ||
207 | <span class="keyword">bool</span> <span class="identifier">successful_modify</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">right</span><span class="special">.</span><span class="identifier">modify_key</span><span class="special">(</span> <span class="identifier">it</span> <span class="special">,</span> <span class="identifier">_key</span> <span class="special">=</span> <span class="string">"1"</span> <span class="special">);</span> | |
208 | ||
209 | <span class="identifier">assert</span><span class="special">(</span> <span class="identifier">successful_modify</span> <span class="special">);</span> | |
210 | <span class="special">}</span> | |
211 | ||
212 | <span class="identifier">bm</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span> <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">(</span><span class="number">2</span><span class="special">,</span><span class="string">"two"</span><span class="special">)</span> <span class="special">);</span> | |
213 | ||
214 | <span class="comment">// Fail to modify (1,"1") to (1,"two") using the left map view</span> | |
215 | <span class="special">{</span> | |
216 | <span class="identifier">assert</span><span class="special">(</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="number">2</span> <span class="special">);</span> | |
217 | ||
218 | <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_iterator</span> <span class="identifier">it</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">find</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> | |
219 | ||
220 | <span class="keyword">bool</span> <span class="identifier">successful_modify</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">modify_data</span><span class="special">(</span> <span class="identifier">it</span><span class="special">,</span> <span class="identifier">_data</span> <span class="special">=</span> <span class="string">"two"</span> <span class="special">);</span> | |
221 | ||
222 | <a class="co" name="boost_bimap.the_tutorial.useful_functions.replace_and_modify.c2" href="useful_functions.html#boost_bimap.the_tutorial.useful_functions.replace_and_modify.c3"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a><span class="identifier">assert</span><span class="special">(</span> <span class="special">!</span> <span class="identifier">successful_modify</span> <span class="special">);</span> | |
223 | <span class="identifier">assert</span><span class="special">(</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="number">1</span> <span class="special">);</span> | |
224 | <span class="special">}</span> | |
225 | </pre> | |
226 | <p> | |
227 | </p> | |
228 | <div class="calloutlist"><table border="0" summary="Callout list"><tr> | |
229 | <td width="5%" valign="top" align="left"><p><a name="boost_bimap.the_tutorial.useful_functions.replace_and_modify.c3"></a><a href="#boost_bimap.the_tutorial.useful_functions.replace_and_modify.c2"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td> | |
230 | <td valign="top" align="left"><p> | |
231 | <code class="computeroutput"><span class="identifier">it</span></code> is not longer valid | |
232 | and <code class="computeroutput"><span class="special">(</span><span class="number">1</span><span class="special">,</span><span class="string">"1"</span><span class="special">)</span></code> is removed from the bimap | |
233 | </p></td> | |
234 | </tr></table></div> | |
235 | </div> | |
236 | <div class="section boost_bimap_the_tutorial_useful_functions_retrieval_of_ranges"> | |
237 | <div class="titlepage"><div><div><h4 class="title"> | |
238 | <a name="boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges"></a><a class="link" href="useful_functions.html#boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges" title="Retrieval of ranges">Retrieval | |
239 | of ranges</a> | |
240 | </h4></div></div></div> | |
241 | <p> | |
242 | Standard <code class="computeroutput"><span class="identifier">lower_bound</span></code> and | |
243 | <code class="computeroutput"><span class="identifier">upper_bound</span></code> functions can | |
244 | be used to lookup for all the elements in a given range. | |
245 | </p> | |
246 | <p> | |
247 | Suppose we want to retrieve the elements from a <code class="computeroutput"><span class="identifier">bimap</span><span class="special"><</span><span class="keyword">int</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">></span></code> where the left value is in the range | |
248 | <code class="computeroutput"><span class="special">[</span><span class="number">20</span><span class="special">,</span><span class="number">50</span><span class="special">]</span></code> | |
249 | </p> | |
250 | <p> | |
251 | </p> | |
252 | <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">bimap</span><span class="special"><</span><span class="keyword">int</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="identifier">bm_type</span><span class="special">;</span> | |
253 | <span class="identifier">bm_type</span> <span class="identifier">bm</span><span class="special">;</span> | |
254 | ||
255 | <span class="comment">// ...</span> | |
256 | ||
257 | <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_iterator</span> <span class="identifier">iter_first</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">lower_bound</span><span class="special">(</span><span class="number">20</span><span class="special">);</span> | |
258 | <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_iterator</span> <span class="identifier">iter_second</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">upper_bound</span><span class="special">(</span><span class="number">50</span><span class="special">);</span> | |
259 | ||
260 | <span class="comment">// range [iter_first,iter_second) contains the elements in [20,50]</span> | |
261 | </pre> | |
262 | <p> | |
263 | </p> | |
264 | <p> | |
265 | Subtle changes to the code are required when strict inequalities are considered. | |
266 | To retrieve the elements greater than 20 and less than 50, the code has | |
267 | to be rewritten as | |
268 | </p> | |
269 | <p> | |
270 | </p> | |
271 | <pre class="programlisting"><span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_iterator</span> <span class="identifier">iter_first</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">upper_bound</span><span class="special">(</span><span class="number">20</span><span class="special">);</span> | |
272 | <span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_iterator</span> <span class="identifier">iter_second</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">lower_bound</span><span class="special">(</span><span class="number">50</span><span class="special">);</span> | |
273 | ||
274 | <span class="comment">// range [iter_first,iter_second) contains the elements in (20,50)</span> | |
275 | </pre> | |
276 | <p> | |
277 | </p> | |
278 | <p> | |
279 | To add to this complexity, the careful programmer has to take into account | |
280 | that the lower and upper bounds of the interval searched be compatible: | |
281 | for instance, if the lower bound is 50 and the upper bound is 20, the iterators | |
282 | <code class="computeroutput"><span class="identifier">iter_first</span></code> and <code class="computeroutput"><span class="identifier">iter_second</span></code> produced by the code above | |
283 | will be in reverse order, with possibly catastrophic results if a traversal | |
284 | from <code class="computeroutput"><span class="identifier">iter_first</span></code> to <code class="computeroutput"><span class="identifier">iter_second</span></code> is tried. All these details | |
285 | make range searching a tedious and error prone task. | |
286 | </p> | |
287 | <p> | |
288 | The range member function, often in combination with lambda expressions, | |
289 | can greatly help alleviate this situation: | |
290 | </p> | |
291 | <p> | |
292 | </p> | |
293 | <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">bimap</span><span class="special"><</span><span class="keyword">int</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="identifier">bm_type</span><span class="special">;</span> | |
294 | <span class="identifier">bm_type</span> <span class="identifier">bm</span><span class="special">;</span> | |
295 | ||
296 | <span class="comment">// ...</span> | |
297 | ||
298 | <a class="co" name="boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c0" href="useful_functions.html#boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c1"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a><span class="identifier">bm_type</span><span class="special">::</span><span class="identifier">left_range_type</span> <span class="identifier">r</span><span class="special">;</span> | |
299 | ||
300 | <a class="co" name="boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c2" href="useful_functions.html#boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c3"><img src="../../../../../../doc/src/images/callouts/2.png" alt="2" border="0"></a><span class="identifier">r</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">range</span><span class="special">(</span> <span class="number">20</span> <span class="special"><=</span> <span class="identifier">_key</span><span class="special">,</span> <span class="identifier">_key</span> <span class="special"><=</span> <span class="number">50</span> <span class="special">);</span> <span class="comment">// [20,50]</span> | |
301 | ||
302 | <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">range</span><span class="special">(</span> <span class="number">20</span> <span class="special"><</span> <span class="identifier">_key</span><span class="special">,</span> <span class="identifier">_key</span> <span class="special"><</span> <span class="number">50</span> <span class="special">);</span> <span class="comment">// (20,50)</span> | |
303 | ||
304 | <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">range</span><span class="special">(</span> <span class="number">20</span> <span class="special"><=</span> <span class="identifier">_key</span><span class="special">,</span> <span class="identifier">_key</span> <span class="special"><</span> <span class="number">50</span> <span class="special">);</span> <span class="comment">// [20,50)</span> | |
305 | </pre> | |
306 | <p> | |
307 | </p> | |
308 | <div class="calloutlist"><table border="0" summary="Callout list"> | |
309 | <tr> | |
310 | <td width="5%" valign="top" align="left"><p><a name="boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c1"></a><a href="#boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c0"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td> | |
311 | <td valign="top" align="left"><p> | |
312 | <code class="computeroutput"><span class="identifier">range_type</span></code> is a handy | |
313 | typedef equal to <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">iterator</span><span class="special">,</span><span class="identifier">iterator</span><span class="special">></span></code>. <code class="computeroutput"><span class="identifier">const_range_type</span></code> | |
314 | is provided too, and it is equal to <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">const_iterator</span><span class="special">,</span><span class="identifier">const_iterator</span><span class="special">></span></code> | |
315 | </p></td> | |
316 | </tr> | |
317 | <tr> | |
318 | <td width="5%" valign="top" align="left"><p><a name="boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c3"></a><a href="#boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c2"><img src="../../../../../../doc/src/images/callouts/2.png" alt="2" border="0"></a> </p></td> | |
319 | <td valign="top" align="left"><p> | |
320 | _key is a Boost.Lambda placeholder. To use it you have to include | |
321 | <code class="computeroutput"><span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">bimap</span><span class="special">/</span><span class="identifier">support</span><span class="special">/</span><span class="identifier">lambda</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> | |
322 | </p></td> | |
323 | </tr> | |
324 | </table></div> | |
325 | <p> | |
326 | <code class="computeroutput"><span class="identifier">range</span></code> simply accepts predicates | |
327 | specifying the lower and upper bounds of the interval searched. Please | |
328 | consult the reference for a detailed explanation of the permissible predicates | |
329 | passed to range. | |
330 | </p> | |
331 | <p> | |
332 | One or both bounds can be omitted with the special unbounded marker: | |
333 | </p> | |
334 | <p> | |
335 | </p> | |
336 | <pre class="programlisting"><span class="identifier">r</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">range</span><span class="special">(</span> <span class="number">20</span> <span class="special"><=</span> <span class="identifier">_key</span><span class="special">,</span> <span class="identifier">unbounded</span> <span class="special">);</span> <span class="comment">// [20,inf)</span> | |
337 | ||
338 | <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">range</span><span class="special">(</span> <span class="identifier">unbounded</span> <span class="special">,</span> <span class="identifier">_key</span> <span class="special"><</span> <span class="number">50</span> <span class="special">);</span> <span class="comment">// (-inf,50)</span> | |
339 | ||
340 | <a class="co" name="boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c4" href="useful_functions.html#boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c5"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a><span class="identifier">r</span> <span class="special">=</span> <span class="identifier">bm</span><span class="special">.</span><span class="identifier">left</span><span class="special">.</span><span class="identifier">range</span><span class="special">(</span> <span class="identifier">unbounded</span> <span class="special">,</span> <span class="identifier">unbounded</span> <span class="special">);</span> <span class="comment">// (-inf,inf)</span> | |
341 | </pre> | |
342 | <p> | |
343 | </p> | |
344 | <div class="calloutlist"><table border="0" summary="Callout list"><tr> | |
345 | <td width="5%" valign="top" align="left"><p><a name="boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c5"></a><a href="#boost_bimap.the_tutorial.useful_functions.retrieval_of_ranges.c4"><img src="../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td> | |
346 | <td valign="top" align="left"><p> | |
347 | This is equivalent to std::make_pair(s.begin(),s.end()) | |
348 | </p></td> | |
349 | </tr></table></div> | |
350 | <p> | |
351 | <a href="../../../../example/tutorial_range.cpp" target="_top">Go to source code</a> | |
352 | </p> | |
353 | </div> | |
354 | </div> | |
355 | <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> | |
356 | <td align="left"></td> | |
357 | <td align="right"><div class="copyright-footer">Copyright © 2006-2012 Matias Capeletto<p> | |
358 | Distributed under the Boost Software License, Version 1.0. (See accompanying | |
359 | 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>) | |
360 | </p> | |
361 | </div></td> | |
362 | </tr></table> | |
363 | <hr> | |
364 | <div class="spirit-nav"> | |
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