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  25 <div class="section">
  26 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
  27 <a name="boost_numericconversion.numeric_converter_policy_classes"></a><a class="link" href="numeric_converter_policy_classes.html" title="Numeric Converter Policy Classes">Numeric
  28     Converter Policy Classes</a>
  29 </h2></div></div></div>
  30 <div class="toc"><dl class="toc">
  31 <dt><span class="section"><a href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.enum_range_check_result">enum
  32       range_check_result</a></span></dt>
  33 <dt><span class="section"><a href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_overflowhandler">Policy
  34       OverflowHandler</a></span></dt>
  35 <dt><span class="section"><a href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder">Policy
  36       Float2IntRounder</a></span></dt>
  37 <dt><span class="section"><a href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_rawconverter">Policy
  38       RawConverter</a></span></dt>
  39 <dt><span class="section"><a href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_userrangechecker">Policy
  40       UserRangeChecker</a></span></dt>
  41 </dl></div>
  42 <div class="section">
  43 <div class="titlepage"><div><div><h3 class="title">
  44 <a name="boost_numericconversion.numeric_converter_policy_classes.enum_range_check_result"></a><a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.enum_range_check_result" title="enum range_check_result">enum
  45       range_check_result</a>
  46 </h3></div></div></div>
  47 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">numeric</span> <span class="special">{</span>
  48
  49     <span class="keyword">enum</span> <span class="identifier">range_check_result</span>
  50     <span class="special">{</span>
  51         <span class="identifier">cInRange</span>     <span class="special">,</span>
  52         <span class="identifier">cNegOverflow</span> <span class="special">,</span>
  53         <span class="identifier">cPosOverflow</span>
  54     <span class="special">}</span> <span class="special">;</span>
  55
  56 <span class="special">}</span> <span class="special">}</span>
  57 </pre>
  58 <p>
  59         Defines the values returned by <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">numeric</span><span class="special">::</span><span class="identifier">converter</span><span class="special">&lt;&gt;::</span><span class="identifier">out_of_range</span><span class="special">()</span></code>
  60       </p>
  61 </div>
  62 <div class="section">
  63 <div class="titlepage"><div><div><h3 class="title">
  64 <a name="boost_numericconversion.numeric_converter_policy_classes.policy_overflowhandler"></a><a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_overflowhandler" title="Policy OverflowHandler">Policy
  65       OverflowHandler</a>
  66 </h3></div></div></div>
  67 <p>
  68         This <span class="emphasis"><em>stateless</em></span> non-template policy class must be a
  69         <span class="emphasis"><em>function object</em></span> and is called to administrate the result
  70         of the range checking. It can throw an exception if overflow has been detected
  71         by the range checking as indicated by its argument. If it throws, is is recommended
  72         that it be <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">bad_cast</span></code> or derived.
  73       </p>
  74 <p>
  75         It must have the following interface (it does not has to be a template class):
  76       </p>
  77 <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">YourOverflowHandlerPolicy</span>
  78 <span class="special">{</span>
  79     <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()</span> <span class="special">(</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_check_result</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// throw bad_cast or derived</span>
  80 <span class="special">}</span> <span class="special">;</span>
  81 </pre>
  82 <p>
  83         It is called with the result of the converter's <code class="computeroutput"><span class="identifier">out_of_range</span><span class="special">()</span></code> inside <code class="computeroutput"><span class="identifier">validate_range</span><span class="special">()</span></code>.
  84       </p>
  85 <p>
  86         These are the two overflow handler classes provided by the library:
  87       </p>
  88 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">numeric</span> <span class="special">{</span>
  89
  90     <span class="keyword">struct</span> <span class="identifier">def_overflow_handler</span>
  91     <span class="special">{</span>
  92         <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()</span> <span class="special">(</span> <span class="identifier">range_check_result</span> <span class="identifier">r</span> <span class="special">)</span> <span class="comment">// throw bad_numeric_conversion derived</span>
  93         <span class="special">{</span>
  94             <span class="keyword">if</span> <span class="special">(</span> <span class="identifier">r</span> <span class="special">==</span> <span class="identifier">cNegOverflow</span> <span class="special">)</span>
  95                 <span class="keyword">throw</span> <span class="identifier">negative_overflow</span><span class="special">()</span> <span class="special">;</span>
  96             <span class="keyword">else</span> <span class="keyword">if</span> <span class="special">(</span> <span class="identifier">r</span> <span class="special">==</span> <span class="identifier">cPosOverflow</span> <span class="special">)</span>
  97                 <span class="keyword">throw</span> <span class="identifier">positive_overflow</span><span class="special">()</span> <span class="special">;</span>
  98         <span class="special">}</span>
  99     <span class="special">}</span> <span class="special">;</span>
 100
 101     <span class="keyword">struct</span> <span class="identifier">silent_overflow_handler</span>
 102     <span class="special">{</span>
 103         <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()</span> <span class="special">(</span> <span class="identifier">range_check_result</span> <span class="special">)</span> <span class="comment">// no-throw</span>
 104         <span class="special">{}</span>
 105     <span class="special">}</span> <span class="special">;</span>
 106
 107 <span class="special">}</span> <span class="special">}</span>
 108 </pre>
 109 <p>
 110         And these are the Exception Classes thrown by the default overflow handler
 111         <a class="link" href="numeric_converter_policy_classes.html#numeric_conversion_policy_overflow_handler_important_note">(see
 112         IMPORTANT note)</a>
 113       </p>
 114 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">numeric</span> <span class="special">{</span>
 115
 116     <a name="numeric_conversion_bad_numeric_cast"></a>
 117     <span class="keyword">class</span> <span class="identifier">bad_numeric_cast</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">bad_cast</span>
 118     <span class="special">{</span>
 119         <span class="keyword">public</span><span class="special">:</span>
 120         <span class="keyword">virtual</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">what</span><span class="special">()</span> <span class="keyword">const</span> <span class="comment">// throw()</span>
 121         <span class="special">{</span>
 122             <span class="keyword">return</span> <span class="string">"bad numeric conversion: overflow"</span><span class="special">;</span>
 123         <span class="special">}</span>
 124
 125     <span class="special">};</span>
 126
 127     <a name="numeric_conversion_negative_overflow"></a>
 128     <span class="keyword">class</span> <span class="identifier">negative_overflow</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">bad_numeric_cast</span>
 129     <span class="special">{</span>
 130         <span class="keyword">public</span><span class="special">:</span>
 131         <span class="keyword">virtual</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">what</span><span class="special">()</span> <span class="keyword">const</span> <span class="comment">// throw()</span>
 132         <span class="special">{</span>
 133             <span class="keyword">return</span> <span class="string">"bad numeric conversion: negative overflow"</span><span class="special">;</span>
 134         <span class="special">}</span>
 135     <span class="special">};</span>
 136
 137     <a name="numeric_conversion_possitive_overflow"></a>
 138     <span class="keyword">class</span> <span class="identifier">positive_overflow</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">bad_numeric_cast</span>
 139     <span class="special">{</span>
 140         <span class="keyword">public</span><span class="special">:</span>
 141         <span class="keyword">virtual</span> <span class="keyword">const</span> <span class="keyword">char</span> <span class="special">*</span><span class="identifier">what</span><span class="special">()</span> <span class="keyword">const</span> <span class="comment">// throw()</span>
 142         <span class="special">{</span>
 143             <span class="keyword">return</span> <span class="string">"bad numeric conversion: positive overflow"</span><span class="special">;</span>
 144         <span class="special">}</span>
 145     <span class="special">};</span>
 146
 147
 148 <span class="special">}</span> <span class="special">}</span>
 149 </pre>
 150 <a name="numeric_conversion_policy_overflow_handler_important_note"></a><div class="important"><table border="0" summary="Important">
 151 <tr>
 152 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td>
 153 <th align="left">Important</th>
 154 </tr>
 155 <tr><td align="left" valign="top"><p>
 156           <span class="bold"><strong>RELEASE NOTE for 1.33</strong></span> Previous to boost
 157           version 1.33, the exception class <code class="computeroutput"><span class="identifier">bad_numeric_cast</span></code>
 158           was named <code class="computeroutput"><span class="identifier">bad_numeric_conversion</span></code>.
 159           However, in 1.33, the old function <code class="computeroutput"><span class="identifier">numeric_cast</span><span class="special">&lt;&gt;</span></code> from <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">cast</span><span class="special">.</span><span class="identifier">hpp</span></code>
 160           was completly replaced by the new <code class="computeroutput"><span class="identifier">numeric_cast</span><span class="special">&lt;&gt;</span></code> in <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">numeric</span><span class="special">/</span><span class="identifier">conversion</span><span class="special">/</span><span class="identifier">cast</span><span class="special">.</span><span class="identifier">hpp</span></code>
 161           (and <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">cast</span><span class="special">.</span><span class="identifier">hpp</span></code> is including <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">numeric</span><span class="special">/</span><span class="identifier">conversion</span><span class="special">/</span><span class="identifier">cast</span><span class="special">.</span><span class="identifier">hpp</span></code>
 162           now). That old function which existed in boost for quite some time used
 163           the <code class="computeroutput"><span class="identifier">bad_numeric_cast</span></code> as
 164           its exception type so I decided to avoid backward compatibility problems
 165           by adopting it (guessing that the user base for the old code is wider than
 166           for the new code).
 167         </p></td></tr>
 168 </table></div>
 169 </div>
 170 <div class="section">
 171 <div class="titlepage"><div><div><h3 class="title">
 172 <a name="boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder"></a><a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder" title="Policy Float2IntRounder">Policy
 173       Float2IntRounder</a>
 174 </h3></div></div></div>
 175 <p>
 176         This <span class="emphasis"><em>stateless</em></span> template policy class specifies the rounding
 177         mode used for <span class="underline">float to integral</span> conversions.
 178         It supplies the <code class="computeroutput"><span class="identifier">nearbyint</span><span class="special">()</span></code> static member function exposed by the converter,
 179         which means that it <span class="underline">publicly inherits from this
 180         policy</span>.
 181       </p>
 182 <p>
 183         The policy must have the following interface:
 184       </p>
 185 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">S</span><span class="special">&gt;</span>
 186 <span class="keyword">struct</span> <span class="identifier">YourFloat2IntRounderPolicy</span>
 187 <span class="special">{</span>
 188     <span class="keyword">typedef</span> <span class="identifier">S</span>               <span class="identifier">source_type</span> <span class="special">;</span>
 189     <span class="keyword">typedef</span> <span class="special">{</span><span class="identifier">S</span> <span class="keyword">or</span> <span class="identifier">S</span> <span class="keyword">const</span><span class="special">&amp;}</span> <span class="identifier">argument_type</span> <span class="special">;</span>
 190
 191     <span class="keyword">static</span> <span class="identifier">source_type</span> <span class="identifier">nearbyint</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span> <span class="special">{</span> <span class="special">...</span> <span class="special">}</span>
 192
 193     <span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">integral_c</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">float_round_style</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">round_</span><span class="special">...&gt;</span> <span class="identifier">round_style</span> <span class="special">;</span>
 194
 195 <span class="special">}</span> <span class="special">;</span>
 196 </pre>
 197 <p>
 198         These are the rounder classes provided by the library (only the specific
 199         parts are shown, see the general policy form above)
 200       </p>
 201 <div class="note"><table border="0" summary="Note">
 202 <tr>
 203 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
 204 <th align="left">Note</th>
 205 </tr>
 206 <tr><td align="left" valign="top"><p>
 207           These classes are not intended to be general purpose rounding functions
 208           but specific policies for <code class="computeroutput"><span class="identifier">converter</span><span class="special">&lt;&gt;</span></code>. This is why they are not function
 209           objects.
 210         </p></td></tr>
 211 </table></div>
 212 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">numeric</span> <span class="special">{</span>
 213
 214
 215     <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">S</span><span class="special">&gt;</span>
 216     <span class="keyword">struct</span> <span class="identifier">Trunc</span>
 217     <span class="special">{</span>
 218         <span class="keyword">static</span> <span class="identifier">source_type</span> <span class="identifier">nearbyint</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
 219         <span class="special">{</span>
 220             <span class="keyword">using</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">floor</span> <span class="special">;</span>
 221             <span class="keyword">using</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">ceil</span>  <span class="special">;</span>
 222
 223             <span class="keyword">return</span> <span class="identifier">s</span> <span class="special">&gt;=</span> <span class="keyword">static_cast</span><span class="special">&lt;</span><span class="identifier">S</span><span class="special">&gt;(</span><span class="number">0</span><span class="special">)</span> <span class="special">?</span> <span class="identifier">floor</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">:</span> <span class="identifier">ceil</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">;</span>
 224         <span class="special">}</span>
 225
 226         <span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">integral_c</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">float_round_style</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">round_toward_zero</span><span class="special">&gt;</span> <span class="identifier">round_style</span> <span class="special">;</span>
 227     <span class="special">}</span> <span class="special">;</span>
 228
 229
 230     <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">S</span><span class="special">&gt;</span>
 231     <span class="keyword">struct</span> <span class="identifier">RoundEven</span>
 232     <span class="special">{</span>
 233         <span class="keyword">static</span> <span class="identifier">source_type</span> <span class="identifier">nearbyint</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
 234         <span class="special">{</span>
 235             <span class="keyword">return</span> <span class="identifier">impl</span><span class="special">-</span><span class="identifier">defined</span><span class="special">-</span><span class="identifier">value</span> <span class="special">;</span>
 236         <span class="special">}</span>
 237
 238         <span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">integral_c</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">float_round_style</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">round_to_nearest</span><span class="special">&gt;</span> <span class="identifier">round_style</span> <span class="special">;</span>
 239     <span class="special">}</span> <span class="special">;</span>
 240
 241
 242     <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">S</span><span class="special">&gt;</span>
 243     <span class="keyword">struct</span> <span class="identifier">Ceil</span>
 244     <span class="special">{</span>
 245         <span class="keyword">static</span> <span class="identifier">source_type</span> <span class="identifier">nearbyint</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
 246         <span class="special">{</span>
 247             <span class="keyword">using</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">ceil</span> <span class="special">;</span>
 248             <span class="keyword">return</span> <span class="identifier">ceil</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">;</span>
 249         <span class="special">}</span>
 250
 251         <span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">integral_c</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">float_round_style</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">round_toward_infinity</span><span class="special">&gt;</span> <span class="identifier">round_style</span> <span class="special">;</span>
 252     <span class="special">}</span> <span class="special">;</span>
 253
 254
 255     <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">S</span><span class="special">&gt;</span>
 256     <span class="keyword">struct</span> <span class="identifier">Floor</span>
 257     <span class="special">{</span>
 258         <span class="keyword">static</span> <span class="identifier">source_type</span> <span class="identifier">nearbyint</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
 259         <span class="special">{</span>
 260             <span class="keyword">using</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">floor</span> <span class="special">;</span>
 261             <span class="keyword">return</span> <span class="identifier">floor</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">;</span>
 262         <span class="special">}</span>
 263         <span class="keyword">typedef</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">integral_c</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">float_round_style</span><span class="special">,</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">round_toward_neg_infinity</span><span class="special">&gt;</span> <span class="identifier">round_style</span> <span class="special">;</span>
 264     <span class="special">}</span> <span class="special">;</span>
 265
 266 <span class="special">}</span> <span class="special">}</span> <span class="comment">// namespace numeric, namespace boost</span>
 267 </pre>
 268 <h5>
 269 <a name="boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder.h0"></a>
 270         <span class="phrase"><a name="boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder.math_functions_used_by_the_rounder_policies"></a></span><a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder.math_functions_used_by_the_rounder_policies">Math
 271         Functions used by the rounder policies</a>
 272       </h5>
 273 <p>
 274         The rounder policies supplied by this header use math functions <code class="computeroutput"><span class="identifier">floor</span><span class="special">()</span></code>
 275         and <code class="computeroutput"><span class="identifier">ceil</span><span class="special">()</span></code>.
 276         The standard versions of these functions are introduced in context by a using
 277         directive, so in normal conditions, the standard functions will be used.
 278       </p>
 279 <p>
 280         However, if there are other visible corresponding overloads an ambiguity
 281         could arise. In this case, the user can supply her own rounder policy which
 282         could, for instance, use a fully qualified call.
 283       </p>
 284 <p>
 285         This technique allows the default rounder policies to be used directly with
 286         user defined types. The user only requires that suitable overloads of <code class="computeroutput"><span class="identifier">floor</span><span class="special">()</span></code>
 287         and <code class="computeroutput"><span class="identifier">ceil</span><span class="special">()</span></code>
 288         be visible. See also <a class="link" href="type_requirements_and_user_defined_types_support.html" title="Type Requirements and User-defined-types support">User
 289         Defined Numeric Types</a> support.
 290       </p>
 291 </div>
 292 <div class="section">
 293 <div class="titlepage"><div><div><h3 class="title">
 294 <a name="boost_numericconversion.numeric_converter_policy_classes.policy_rawconverter"></a><a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_rawconverter" title="Policy RawConverter">Policy
 295       RawConverter</a>
 296 </h3></div></div></div>
 297 <p>
 298         This <span class="emphasis"><em>stateless</em></span> template policy class is used to perform
 299         the actual conversion from Source to Target. It supplies the <code class="computeroutput"><span class="identifier">low_level_convert</span><span class="special">()</span></code>
 300         static member function exposed by the converter, which means that it publicly
 301         inherits from this policy.
 302       </p>
 303 <p>
 304         The policy must have the following interface:
 305       </p>
 306 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Traits</span><span class="special">&gt;</span>
 307 <span class="keyword">struct</span> <span class="identifier">YourRawConverterPolicy</span>
 308 <span class="special">{</span>
 309     <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">result_type</span>   <span class="identifier">result_type</span>   <span class="special">;</span>
 310     <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">argument_type</span> <span class="identifier">argument_type</span> <span class="special">;</span>
 311
 312     <span class="keyword">static</span> <span class="identifier">result_type</span> <span class="identifier">low_level_convert</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="special">&lt;</span><span class="identifier">impl</span> <span class="identifier">defined</span><span class="special">&gt;</span> <span class="special">;</span> <span class="special">}</span>
 313 <span class="special">}</span> <span class="special">;</span>
 314 </pre>
 315 <p>
 316         This policy is mostly provided as a hook for user defined types which don't
 317         support <code class="computeroutput"><span class="keyword">static_cast</span><span class="special">&lt;&gt;</span></code>
 318         conversions to some types
 319       </p>
 320 <p>
 321         This is the only raw converter policy class provided by the library:
 322       </p>
 323 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">numeric</span> <span class="special">{</span>
 324
 325     <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Traits</span><span class="special">&gt;</span>
 326     <span class="keyword">struct</span> <span class="identifier">raw_numeric_converter</span>
 327     <span class="special">{</span>
 328         <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">result_type</span>   <span class="identifier">result_type</span>   <span class="special">;</span>
 329         <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">argument_type</span> <span class="identifier">argument_type</span> <span class="special">;</span>
 330
 331         <span class="keyword">static</span> <span class="identifier">result_type</span> <span class="identifier">low_level_convert</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
 332         <span class="special">{</span>
 333             <span class="keyword">return</span> <span class="keyword">static_cast</span><span class="special">&lt;</span><span class="identifier">result_type</span><span class="special">&gt;(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">;</span>
 334         <span class="special">}</span>
 335     <span class="special">}</span> <span class="special">;</span>
 336
 337 <span class="special">}</span> <span class="special">}</span>
 338 </pre>
 339 </div>
 340 <div class="section">
 341 <div class="titlepage"><div><div><h3 class="title">
 342 <a name="boost_numericconversion.numeric_converter_policy_classes.policy_userrangechecker"></a><a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_userrangechecker" title="Policy UserRangeChecker">Policy
 343       UserRangeChecker</a>
 344 </h3></div></div></div>
 345 <p>
 346         This <span class="emphasis"><em>stateless</em></span> template policy class is used <span class="underline">only if supplied</span> to <span class="bold"><strong>override</strong></span>
 347         the internal range checking logic.
 348       </p>
 349 <p>
 350         It supplies the <code class="computeroutput"><span class="identifier">validate_range</span><span class="special">()</span></code> static member function exposed by the converter,
 351         which means that it publicly inherits from this policy.
 352       </p>
 353 <p>
 354         The policy must have the following interface:
 355       </p>
 356 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Traits</span><span class="special">&gt;</span>
 357 <span class="keyword">struct</span> <span class="identifier">YourRangeCheckerPolicy</span>
 358 <span class="special">{</span>
 359     <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">argument_type</span> <span class="identifier">argument_type</span> <span class="special">;</span>
 360
 361     <span class="comment">// Determines if the value 's' fits in the range of the Target type.</span>
 362     <span class="keyword">static</span> <span class="identifier">range_check_result</span> <span class="identifier">out_of_range</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span> <span class="special">;</span>
 363
 364     <span class="comment">// Checks whether the value 's' is out_of_range()</span>
 365     <span class="comment">// and passes the result of the check to the OverflowHandler policy.</span>
 366     <span class="keyword">static</span> <span class="keyword">void</span> <span class="identifier">validate_range</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
 367     <span class="special">{</span>
 368         <span class="identifier">OverflowHandler</span><span class="special">()(</span> <span class="identifier">out_of_range</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
 369     <span class="special">}</span>
 370 <span class="special">}</span> <span class="special">;</span>
 371 </pre>
 372 <p>
 373         This policy is <span class="bold"><strong>only</strong></span> provided as a hook for
 374         user defined types which require range checking (which is disabled by default
 375         when a UDT is involved). The library provides a class: <code class="computeroutput"><span class="identifier">UseInternalRangeChecker</span><span class="special">{}</span></code>; which is a <span class="emphasis"><em>fake</em></span>
 376         <code class="computeroutput"><span class="identifier">RangeChecker</span></code> policy used
 377         to signal the converter to use its internal range checking implementation.
 378       </p>
 379 </div>
 380 </div>
 381 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 382 <td align="left"></td>
 383 <td align="right"><div class="copyright-footer">Copyright &#169; 2004-2007 Fernando
 384       Luis Cacciola Carballal<p>
 385         Distributed under the Boost Software License, Version 1.0. (See accompanying
 386         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>)
 387       </p>
 388 </div></td>
 389 </tr></table>
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