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converter___function_object.html

converter___function_object.html 35 KB
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  25. <div class="section">
    26. 

  26. <div class="titlepage"><div><div><h2 class="title" style="clear: both">
    27. 

  27. <a name="boost_numericconversion.converter___function_object"></a><a class="link" href="converter___function_object.html" title="converter&lt;&gt; function object">converter&lt;&gt;
    28. 

  28.     function object</a>
    29. 

  29. </h2></div></div></div>
    30. 

  30. <div class="toc"><dl class="toc">
    31. 

  31. <dt><span class="section"><a href="converter___function_object.html#boost_numericconversion.converter___function_object.synopsis">Synopsis</a></span></dt>
    32. 

  32. <dt><span class="section"><a href="converter___function_object.html#boost_numericconversion.converter___function_object.template_parameters">Template
    33. 

  33.       parameters</a></span></dt>
    34. 

  34. <dt><span class="section"><a href="converter___function_object.html#boost_numericconversion.converter___function_object.member_functions">Member
    35. 

  35.       functions</a></span></dt>
    36. 

  36. <dt><span class="section"><a href="converter___function_object.html#boost_numericconversion.converter___function_object.range_checking_logic">Range
    37. 

  37.       Checking Logic</a></span></dt>
    38. 

  38. <dt><span class="section"><a href="converter___function_object.html#boost_numericconversion.converter___function_object.examples">Examples</a></span></dt>
    39. 

  39. </dl></div>
    40. 

  40. <div class="section">
    41. 

  41. <div class="titlepage"><div><div><h3 class="title">
    42. 

  42. <a name="boost_numericconversion.converter___function_object.synopsis"></a><a class="link" href="converter___function_object.html#boost_numericconversion.converter___function_object.synopsis" title="Synopsis">Synopsis</a>
    43. 

  43. </h3></div></div></div>
    44. 

  44. <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>
    45. 

  45. 

  46. 

  47.     <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span>
    48. 

  48.              <span class="keyword">class</span> <span class="identifier">S</span><span class="special">,</span>
    49. 

  49.              <span class="keyword">class</span> <span class="identifier">Traits</span><span class="special">,</span>          <span class="special">=</span> <span class="identifier">conversion_traits</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">,</span><span class="identifier">S</span><span class="special">&gt;</span>
    50. 

  50.              <span class="keyword">class</span> <span class="identifier">OverflowHandler</span>  <span class="special">=</span> <span class="identifier">def_overflow_handler</span><span class="special">,</span>
    51. 

  51.              <span class="keyword">class</span> <span class="identifier">Float2IntRounder</span> <span class="special">=</span> <span class="identifier">Trunc</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">source_type</span> <span class="special">&gt;,</span>
    52. 

  52.              <span class="keyword">class</span> <span class="identifier">RawConverter</span>     <span class="special">=</span> <span class="identifier">raw_converter</span><span class="special">&lt;</span><span class="identifier">Traits</span><span class="special">&gt;,</span>
    53. 

  53.              <span class="keyword">class</span> <span class="identifier">UserRangeChecker</span> <span class="special">=</span> <span class="identifier">UseInternalRangeChecker</span>
    54. 

  54.             <span class="special">&gt;</span>
    55. 

  55.     <span class="keyword">struct</span> <span class="identifier">converter</span>
    56. 

  56.     <span class="special">{</span>
    57. 

  57.         <span class="keyword">typedef</span> <span class="identifier">Traits</span> <span class="identifier">traits</span> <span class="special">;</span>
    58. 

  58. 

  59.         <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Traits</span><span class="special">::</span><span class="identifier">source_type</span>   <span class="identifier">source_type</span>   <span class="special">;</span>
    60. 

  60.         <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>
    61. 

  61.         <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>
    62. 

  62. 

  63.         <span class="keyword">static</span> <span class="identifier">result_type</span> <span class="identifier">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>
    64. 

  64. 

  65.         <span class="identifier">result_type</span> <span class="keyword">operator</span><span class="special">()</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span>
    66. 

  66. 

  67.         <span class="comment">// Internal member functions:</span>
    68. 

  68. 

  69.         <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>
    70. 

  70.         <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> <span class="special">;</span>
    71. 

  71.         <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>
    72. 

  72.         <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>
    73. 

  73. 

  74.     <span class="special">}</span> <span class="special">;</span>
    75. 

  75. 

  76. <span class="special">}</span> <span class="special">}</span> <span class="comment">// namespace numeric, boost</span>
    77. 

  77. </pre>
    78. 

  78. <p>
    79. 

  79.         <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></code>
    80. 

  80.         is a <a href="http://www.sgi.com/tech/stl/UnaryFunction.html" target="_top">Unary Function
    81. 

  81.         Object</a> encapsulating the code to perform a numeric conversion with
    82. 

  82.         the direction and properties specified by the Traits template parameter.
    83. 

  83.         It can optionally take some <a class="link" href="numeric_converter_policy_classes.html" title="Numeric Converter Policy Classes">policies</a>
    84. 

  84.         which can be used to customize its behavior. The <code class="computeroutput"><span class="identifier">Traits</span></code>
    85. 

  85.         parameter is not a policy but the parameter that defines the conversion.
    86. 

  86.       </p>
    87. 

  87. </div>
    88. 

  88. <div class="section">
    89. 

  89. <div class="titlepage"><div><div><h3 class="title">
    90. 

  90. <a name="boost_numericconversion.converter___function_object.template_parameters"></a><a class="link" href="converter___function_object.html#boost_numericconversion.converter___function_object.template_parameters" title="Template parameters">Template
    91. 

  91.       parameters</a>
    92. 

  92. </h3></div></div></div>
    93. 

  93. <div class="informaltable"><table class="table">
    94. 

  94. <colgroup>
    95. 

  95. <col>
    96. 

  96. <col>
    97. 

  97. </colgroup>
    98. 

  98. <thead><tr>
    99. 

  99. <th>
    100. 

  100.               </th>
    101. 

  101. <th>
    102. 

  102.               </th>
    103. 

  103. </tr></thead>
    104. 

  104. <tbody>
    105. 

  105. <tr>
    106. 

  106. <td>
    107. 

  107.                 <p>
    108. 

  108.                   <code class="computeroutput"><span class="identifier">T</span></code>
    109. 

  109.                 </p>
    110. 

  110.               </td>
    111. 

  111. <td>
    112. 

  112.                 <p>
    113. 

  113.                   The <a class="link" href="definitions.html#boost_numericconversion.definitions.numeric_types" title="Numeric Types">Numeric
    114. 

  114.                   Type</a> which is the <span class="emphasis"><em>Target</em></span> of the conversion.
    115. 

  115.                 </p>
    116. 

  116.               </td>
    117. 

  117. </tr>
    118. 

  118. <tr>
    119. 

  119. <td>
    120. 

  120.                 <p>
    121. 

  121.                   <code class="computeroutput"><span class="identifier">S</span></code>
    122. 

  122.                 </p>
    123. 

  123.               </td>
    124. 

  124. <td>
    125. 

  125.                 <p>
    126. 

  126.                   The <a class="link" href="definitions.html#boost_numericconversion.definitions.numeric_types" title="Numeric Types">Numeric
    127. 

  127.                   Type</a> which is the <span class="emphasis"><em>Source</em></span> of the conversion.
    128. 

  128.                 </p>
    129. 

  129.               </td>
    130. 

  130. </tr>
    131. 

  131. <tr>
    132. 

  132. <td>
    133. 

  133.                 <p>
    134. 

  134.                   <code class="computeroutput"><span class="identifier">Traits</span></code>
    135. 

  135.                 </p>
    136. 

  136.               </td>
    137. 

  137. <td>
    138. 

  138.                 <p>
    139. 

  139.                   This must be a conversion traits class with the interface of <a class="link" href="conversion_traits___traits_class.html" title="conversion_traits&lt;&gt; traits class"><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_traits</span></code></a>
    140. 

  140.                 </p>
    141. 

  141.               </td>
    142. 

  142. </tr>
    143. 

  143. <tr>
    144. 

  144. <td>
    145. 

  145.                 <p>
    146. 

  146.                   <code class="computeroutput"><span class="identifier">OverflowHandler</span></code>
    147. 

  147.                 </p>
    148. 

  148.               </td>
    149. 

  149. <td>
    150. 

  150.                 <p>
    151. 

  151.                   <span class="bold"><strong>Stateless Policy</strong></span> called to administrate
    152. 

  152.                   the result of the range checking.
    153. 

  153.                 </p>
    154. 

  154.                 <p>
    155. 

  155.                   It is a <span class="bold"><strong>Function Object</strong></span> which
    156. 

  156.                   receives the result of <code class="computeroutput"><span class="identifier">out_of_range</span><span class="special">()</span></code> and is called inside the <code class="computeroutput"><span class="identifier">validate_range</span><span class="special">()</span></code>
    157. 

  157.                   static member function exposed by the converter.
    158. 

  158.                 </p>
    159. 

  159.               </td>
    160. 

  160. </tr>
    161. 

  161. <tr>
    162. 

  162. <td>
    163. 

  163.                 <p>
    164. 

  164.                   <code class="computeroutput"><span class="identifier">Float2IntRounder</span></code>
    165. 

  165.                 </p>
    166. 

  166.               </td>
    167. 

  167. <td>
    168. 

  168.                 <p>
    169. 

  169.                   <span class="bold"><strong>Stateless Policy</strong></span> which specifies
    170. 

  170.                   the rounding mode used for float to integral conversions.
    171. 

  171.                 </p>
    172. 

  172.                 <p>
    173. 

  173.                   It supplies the <code class="computeroutput"><span class="identifier">nearbyint</span><span class="special">()</span></code> static member function exposed
    174. 

  174.                   by the converter.
    175. 

  175.                 </p>
    176. 

  176.               </td>
    177. 

  177. </tr>
    178. 

  178. <tr>
    179. 

  179. <td>
    180. 

  180.                 <p>
    181. 

  181.                   <code class="computeroutput"><span class="identifier">RawConverter</span></code>
    182. 

  182.                 </p>
    183. 

  183.               </td>
    184. 

  184. <td>
    185. 

  185.                 <p>
    186. 

  186.                   <span class="bold"><strong>Stateless Policy</strong></span> which is used
    187. 

  187.                   to perform the actual conversion.
    188. 

  188.                 </p>
    189. 

  189.                 <p>
    190. 

  190.                   It supplies the <code class="computeroutput"><span class="identifier">low_level_convert</span><span class="special">()</span></code> static member function exposed
    191. 

  191.                   by the converter.
    192. 

  192.                 </p>
    193. 

  193.               </td>
    194. 

  194. </tr>
    195. 

  195. <tr>
    196. 

  196. <td>
    197. 

  197.                 <p>
    198. 

  198.                   <code class="computeroutput"><span class="identifier">UserRangeChecker</span></code>
    199. 

  199.                 </p>
    200. 

  200.               </td>
    201. 

  201. <td>
    202. 

  202.                 <p>
    203. 

  203.                   <span class="emphasis"><em>Special and Optional</em></span> <span class="bold"><strong>Stateless
    204. 

  204.                   Policy</strong></span> which can be used to override the internal range
    205. 

  205.                   checking logic.
    206. 

  206.                 </p>
    207. 

  207.                 <p>
    208. 

  208.                   If given, supplies alternative code for the <code class="computeroutput"><span class="identifier">out_of_range</span><span class="special">()</span></code> and <code class="computeroutput"><span class="identifier">validate_range</span><span class="special">()</span></code> static member functions exposed
    209. 

  209.                   by the converter.
    210. 

  210.                 </p>
    211. 

  211.               </td>
    212. 

  212. </tr>
    213. 

  213. </tbody>
    214. 

  214. </table></div>
    215. 

  215. </div>
    216. 

  216. <div class="section">
    217. 

  217. <div class="titlepage"><div><div><h3 class="title">
    218. 

  218. <a name="boost_numericconversion.converter___function_object.member_functions"></a><a class="link" href="converter___function_object.html#boost_numericconversion.converter___function_object.member_functions" title="Member functions">Member
    219. 

  219.       functions</a>
    220. 

  220. </h3></div></div></div>
    221. 

  221. <div class="blockquote"><blockquote class="blockquote"><p>
    222. 

  222.           <code class="computeroutput"><span class="keyword">static</span> <span class="identifier">result_type</span>
    223. 

  223.           <span class="identifier">converter</span><span class="special">&lt;&gt;::</span><span class="identifier">convert</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span>
    224. 

  224.           <span class="special">)</span> <span class="special">;</span> <span class="comment">// throw</span> </code>
    225. 

  225.         </p></blockquote></div>
    226. 

  226. <p>
    227. 

  227.         This static member function converts an rvalue of type <code class="computeroutput"><span class="identifier">source_type</span></code>
    228. 

  228.         to an rvalue of type <code class="computeroutput"><span class="identifier">target_type</span></code>.
    229. 

  229.       </p>
    230. 

  230. <p>
    231. 

  231.         If the conversion requires it, it performs a range checking before the conversion
    232. 

  232.         and passes the result of the check to the overflow handler policy (the default
    233. 

  233.         policy throws an exception if out-of-range is detected)
    234. 

  234.       </p>
    235. 

  235. <p>
    236. 

  236.         The implementation of this function is actually built from the policies and
    237. 

  237.         is basically as follows:
    238. 

  238.       </p>
    239. 

  239. <pre class="programlisting"><span class="identifier">result_type</span> <span class="identifier">converter</span><span class="special">&lt;&gt;::</span><span class="identifier">convert</span> <span class="special">(</span> <span class="identifier">argument_type</span> <span class="identifier">s</span> <span class="special">)</span>
    240. 

  240. <span class="special">{</span>
    241. 

  241.     <span class="identifier">validate_range</span><span class="special">(</span><span class="identifier">s</span><span class="special">);</span> <span class="comment">// Implemented by the internal range checking logic</span>
    242. 

  242.                        <span class="comment">// (which also calls the OverflowHandler policy)</span>
    243. 

  243.                        <span class="comment">// or externally supplied by the UserRangeChecker policy.</span>
    244. 

  244. 

  245.     <span class="identifier">s</span> <span class="special">=</span> <span class="identifier">nearbyint</span><span class="special">(</span><span class="identifier">s</span><span class="special">);</span> <span class="comment">// Externally supplied by the Float2IntRounder policy.</span>
    246. 

  246.                       <span class="comment">// NOTE: This is actually called only for float to int conversions.</span>
    247. 

  247. 

  248.     <span class="keyword">return</span> <span class="identifier">low_level_convert</span><span class="special">(</span><span class="identifier">s</span><span class="special">);</span> <span class="comment">// Externally supplied by the RawConverter policy.</span>
    249. 

  249. <span class="special">}</span>
    250. 

  250. </pre>
    251. 

  251. <p>
    252. 

  252.         <code class="computeroutput"><span class="identifier">converter</span><span class="special">&lt;&gt;::</span><span class="keyword">operator</span><span class="special">()</span> <span class="keyword">const</span></code> just calls <code class="computeroutput"><span class="identifier">convert</span><span class="special">()</span></code>
    253. 

  253.       </p>
    254. 

  254. <p>
    255. 

  255.         <span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
    256. 

  256.       </p>
    257. 

  257. <div class="blockquote"><blockquote class="blockquote"><p>
    258. 

  258.           <code class="computeroutput"><span class="keyword">static</span> <span class="identifier">range_check_result</span>
    259. 

  259.           <span class="identifier">numeric_converter</span><span class="special">&lt;&gt;::</span><span class="identifier">out_of_range</span> <span class="special">(</span>
    260. 

  260.           <span class="identifier">argument_type</span> <span class="identifier">s</span>
    261. 

  261.           <span class="special">)</span> <span class="special">;</span></code>
    262. 

  262.         </p></blockquote></div>
    263. 

  263. <p>
    264. 

  264.         This <a class="link" href="converter___function_object.html#numeric_conversion_converter_internal">internal</a>
    265. 

  265.         static member function determines if the value <code class="computeroutput"><span class="identifier">s</span></code>
    266. 

  266.         can be represented by the target type without overflow.
    267. 

  267.       </p>
    268. 

  268. <p>
    269. 

  269.         It does not determine if the conversion is <span class="emphasis"><em>exact</em></span>; that
    270. 

  270.         is, it does not detect <span class="emphasis"><em>inexact</em></span> conversions, only <span class="emphasis"><em>out-of-range</em></span>
    271. 

  271.         conversions (see the <a class="link" href="definitions.html#boost_numericconversion.definitions.exact__correctly_rounded_and_out_of_range_representations" title="Exact, Correctly Rounded and Out-Of-Range Representations">Definitions</a>
    272. 

  272.         for further details).
    273. 

  273.       </p>
    274. 

  274. <p>
    275. 

  275.         The return value is of enum type <a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.enum_range_check_result" title="enum range_check_result"><code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">numeric</span><span class="special">::</span><span class="identifier">range_check_result</span></code></a>
    276. 

  276.       </p>
    277. 

  277. <p>
    278. 

  278.         The actual code for the range checking logic is optimized for the combined
    279. 

  279.         properties of the source and target types. For example, a non-subranged conversion
    280. 

  280.         (i.e: <code class="computeroutput"><span class="keyword">int</span></code>-&gt;<code class="computeroutput"><span class="keyword">float</span></code>), requires no range checking, so <code class="computeroutput"><span class="identifier">out_of_range</span><span class="special">()</span></code>
    281. 

  281.         returns <code class="computeroutput"><span class="identifier">cInRange</span></code> directly.
    282. 

  282.         See the following <a class="link" href="converter___function_object.html#boost_numericconversion.converter___function_object.range_checking_logic" title="Range Checking Logic">table</a>
    283. 

  283.         for more details.
    284. 

  284.       </p>
    285. 

  285. <p>
    286. 

  286.         If the user supplied a <a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_userrangechecker" title="Policy UserRangeChecker">UserRangeChecker</a>
    287. 

  287.         policy, is this policy which implements this function, so the implementation
    288. 

  288.         is user defined, although it is expected to perform the same conceptual check
    289. 

  289.         and return the appropriate result.
    290. 

  290.       </p>
    291. 

  291. <p>
    292. 

  292.         <span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
    293. 

  293.       </p>
    294. 

  294. <div class="blockquote"><blockquote class="blockquote"><p>
    295. 

  295.           <code class="computeroutput"><span class="keyword">static</span> <span class="keyword">void</span>
    296. 

  296.           <span class="identifier">numeric_converter</span><span class="special">&lt;&gt;::</span><span class="identifier">validate_range</span> <span class="special">(</span>
    297. 

  297.           <span class="identifier">argument_type</span> <span class="identifier">s</span>
    298. 

  298.           <span class="special">)</span> <span class="special">;</span> <span class="comment">// no throw</span> </code>
    299. 

  299.         </p></blockquote></div>
    300. 

  300. <p>
    301. 

  301.         This <a class="link" href="converter___function_object.html#numeric_conversion_converter_internal">internal</a>
    302. 

  302.         static member function calls out_of_range(s), and passes the result to the
    303. 

  303.         <a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_overflowhandler" title="Policy OverflowHandler">OverflowHandler</a>
    304. 

  304.         policy class.
    305. 

  305.       </p>
    306. 

  306. <p>
    307. 

  307.         For those Target/Source combinations which don't require range checking,
    308. 

  308.         this is an empty inline function.
    309. 

  309.       </p>
    310. 

  310. <p>
    311. 

  311.         If the user supplied a <a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_userrangechecker" title="Policy UserRangeChecker">UserRangeChecker</a>
    312. 

  312.         policy, is this policy which implements this function, so the implementation
    313. 

  313.         is user defined, although it is expected to perform the same action as the
    314. 

  314.         default. In particular, it is expected to pass the result of the check to
    315. 

  315.         the overflow handler.
    316. 

  316.       </p>
    317. 

  317. <p>
    318. 

  318.         <span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
    319. 

  319.       </p>
    320. 

  320. <div class="blockquote"><blockquote class="blockquote"><p>
    321. 

  321.           <code class="computeroutput"><span class="keyword">static</span> <span class="identifier">result_type</span>
    322. 

  322.           <span class="identifier">numeric_converter</span><span class="special">&lt;&gt;::</span><span class="identifier">low_level_convert</span> <span class="special">(</span>
    323. 

  323.           <span class="identifier">argument_type</span> <span class="identifier">s</span>
    324. 

  324.           <span class="special">)</span> <span class="special">;</span></code>
    325. 

  325.         </p></blockquote></div>
    326. 

  326. <p>
    327. 

  327.         This <a class="link" href="converter___function_object.html#numeric_conversion_converter_internal">internal</a>
    328. 

  328.         static member function performs the actual conversion.
    329. 

  329.       </p>
    330. 

  330. <p>
    331. 

  331.         This function is externally supplied by the <a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_rawconverter" title="Policy RawConverter">RawConverter</a>
    332. 

  332.         policy class.
    333. 

  333.       </p>
    334. 

  334. <p>
    335. 

  335.         <span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
    336. 

  336.       </p>
    337. 

  337. <div class="blockquote"><blockquote class="blockquote"><p>
    338. 

  338.           <code class="computeroutput"><span class="keyword">static</span> <span class="identifier">source_type</span>
    339. 

  339.           <span class="identifier">converter</span><span class="special">&lt;&gt;::</span><span class="identifier">nearbyint</span> <span class="special">(</span>
    340. 

  340.           <span class="identifier">argument_type</span> <span class="identifier">s</span>
    341. 

  341.           <span class="special">)</span> <span class="special">;</span></code>
    342. 

  342.         </p></blockquote></div>
    343. 

  343. <p>
    344. 

  344.         This <a class="link" href="converter___function_object.html#numeric_conversion_converter_internal">internal</a>
    345. 

  345.         static member function, which is <span class="underline">only used</span>
    346. 

  346.         for <code class="computeroutput"><span class="keyword">float</span></code> to <code class="computeroutput"><span class="keyword">int</span></code>
    347. 

  347.         conversions, returns an <span class="emphasis"><em>integer</em></span> value of <span class="emphasis"><em><span class="underline">floating-point type</span></em></span> according to some
    348. 

  348.         rounding direction.
    349. 

  349.       </p>
    350. 

  350. <p>
    351. 

  351.         This function is externally supplied by the <a class="link" href="numeric_converter_policy_classes.html#boost_numericconversion.numeric_converter_policy_classes.policy_float2introunder" title="Policy Float2IntRounder">Float2IntRounder</a>
    352. 

  352.         policy class which encapsulates the specific rounding mode.
    353. 

  353.       </p>
    354. 

  354. <p>
    355. 

  355.         <span class="inlinemediaobject"><img src="../images/space.png" alt="space"></span>
    356. 

  356.       </p>
    357. 

  357. <a name="numeric_conversion_converter_internal"></a><h5>
    358. 

  358. <a name="boost_numericconversion.converter___function_object.member_functions.h0"></a>
    359. 

  359.         <span class="phrase"><a name="boost_numericconversion.converter___function_object.member_functions.internal_member_functions"></a></span><a class="link" href="converter___function_object.html#boost_numericconversion.converter___function_object.member_functions.internal_member_functions">Internal
    360. 

  360.         Member Functions</a>
    361. 

  361.       </h5>
    362. 

  362. <p>
    363. 

  363.         These static member functions build the actual conversion code used by <code class="computeroutput"><span class="identifier">convert</span><span class="special">()</span></code>.
    364. 

  364.         The user does not have to call these if calling <code class="computeroutput"><span class="identifier">convert</span><span class="special">()</span></code>, since <code class="computeroutput"><span class="identifier">convert</span><span class="special">()</span></code> calls them infernally, but they can be
    365. 

  365.         called separately for specific needs.
    366. 

  366.       </p>
    367. 

  367. </div>
    368. 

  368. <div class="section">
    369. 

  369. <div class="titlepage"><div><div><h3 class="title">
    370. 

  370. <a name="boost_numericconversion.converter___function_object.range_checking_logic"></a><a class="link" href="converter___function_object.html#boost_numericconversion.converter___function_object.range_checking_logic" title="Range Checking Logic">Range
    371. 

  371.       Checking Logic</a>
    372. 

  372. </h3></div></div></div>
    373. 

  373. <p>
    374. 

  374.         The following table summarizes the internal range checking logic performed
    375. 

  375.         for each combination of the properties of Source and Target.
    376. 

  376.       </p>
    377. 

  377. <p>
    378. 

  378.         LowestT/HighestT denotes the highest and lowest values of the Target type,
    379. 

  379.         respectively.
    380. 

  380.       </p>
    381. 

  381. <p>
    382. 

  382.         <code class="computeroutput"><span class="identifier">S</span><span class="special">(</span><span class="identifier">n</span><span class="special">)</span></code> is short
    383. 

  383.         for <code class="computeroutput"><span class="keyword">static_cast</span><span class="special">&lt;</span><span class="identifier">S</span><span class="special">&gt;(</span><span class="identifier">n</span><span class="special">)</span></code> (<code class="computeroutput"><span class="identifier">S</span></code> denotes the Source type).
    384. 

  384.       </p>
    385. 

  385. <p>
    386. 

  386.         <code class="computeroutput"><span class="identifier">NONE</span></code> indicates that for this
    387. 

  387.         case there is no range checking.
    388. 

  388.       </p>
    389. 

  389. <pre class="programlisting"><code class="literal">
    390. 

  390. int_to_int    |--&gt; sig_to_sig     |--&gt; subranged     |--&gt; ( s &gt;= S(LowestT) ) &amp;&amp; ( s &lt;= S(HighestT) )
    391. 

  391.               |                   |--&gt; not subranged |--&gt; NONE
    392. 

  392.               |
    393. 

  393.               |--&gt; unsig_to_unsig |--&gt; subranged     |--&gt; ( s &gt;= S(LowestT) ) &amp;&amp; ( s &lt;= S(HighestT) )
    394. 

  394.               |                   |--&gt; not subranged |--&gt; NONE
    395. 

  395.               |
    396. 

  396.               |--&gt; sig_to_unsig   |--&gt; pos subranged     |--&gt; ( s &gt;= S(0) ) &amp;&amp; ( s &lt;= S(HighestT) )
    397. 

  397.               |                   |--&gt; not pos subranged |--&gt; ( s &gt;= S(0) )
    398. 

  398.               |
    399. 

  399.               |--&gt; unsig_to_sig   |--&gt; subranged     |--&gt; ( s &lt;= S(HighestT) )
    400. 

  400.               |                   |--&gt; not subranged |--&gt; NONE
    401. 

  401. </code>
    402. 

  402. <code class="literal">
    403. 

  403. int_to_float   |--&gt; NONE
    404. 

  404. </code>
    405. 

  405. <code class="literal">
    406. 

  406. float_to_int   |--&gt; round_to_zero         |--&gt; ( s &gt;  S(LowestT)-S(1)   ) &amp;&amp; ( s &lt;  S(HighestT)+S(1)   )
    407. 

  407.                |--&gt; round_to_even_nearest |--&gt; ( s &gt;= S(LowestT)-S(0.5) ) &amp;&amp; ( s &lt;  S(HighestT)+S(0.5) )
    408. 

  408.                |--&gt; round_to_infinity     |--&gt; ( s &gt;  S(LowestT)-S(1)   ) &amp;&amp; ( s &lt;= S(HighestT)        )
    409. 

  409.                |--&gt; round_to_neg_infinity |--&gt; ( s &gt;= S(LowestT)        ) &amp;&amp; ( s &lt;  S(HighestT)+S(1)   )
    410. 

  410. </code>
    411. 

  411. <code class="literal">
    412. 

  412. float_to_float |--&gt; subranged     |--&gt; ( s &gt;= S(LowestT) ) &amp;&amp; ( s &lt;= S(HighestT) )
    413. 

  413.                |--&gt; not subranged |--&gt; NONE
    414. 

  414. </code>
    415. 

  415. </pre>
    416. 

  416. </div>
    417. 

  417. <div class="section">
    418. 

  418. <div class="titlepage"><div><div><h3 class="title">
    419. 

  419. <a name="boost_numericconversion.converter___function_object.examples"></a><a class="link" href="converter___function_object.html#boost_numericconversion.converter___function_object.examples" title="Examples">Examples</a>
    420. 

  420. </h3></div></div></div>
    421. 

  421. <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">cassert</span><span class="special">&gt;</span>
    422. 

  422. <span class="preprocessor">#include</span> <span class="special">&lt;</span><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">converter</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
    423. 

  423. 

  424. <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> <span class="special">{</span>
    425. 

  425. 

  426.     <span class="keyword">typedef</span> <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;</span><span class="keyword">int</span><span class="special">,</span><span class="keyword">double</span><span class="special">&gt;</span> <span class="identifier">Double2Int</span> <span class="special">;</span>
    427. 

  427. 

  428.     <span class="keyword">int</span> <span class="identifier">x</span> <span class="special">=</span> <span class="identifier">Double2Int</span><span class="special">::</span><span class="identifier">convert</span><span class="special">(</span><span class="number">2.0</span><span class="special">);</span>
    429. 

  429.     <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">x</span> <span class="special">==</span> <span class="number">2</span> <span class="special">);</span>
    430. 

  430. 

  431.     <span class="keyword">int</span> <span class="identifier">y</span> <span class="special">=</span> <span class="identifier">Double2Int</span><span class="special">()(</span><span class="number">3.14</span><span class="special">);</span> <span class="comment">// As a function object.</span>
    432. 

  432.     <span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">y</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// The default rounding is trunc.</span>
    433. 

  433. 

  434.     <span class="keyword">try</span>
    435. 

  435.     <span class="special">{</span>
    436. 

  436.         <span class="keyword">double</span> <span class="identifier">m</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">numeric</span><span class="special">::</span><span class="identifier">bounds</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;::</span><span class="identifier">highest</span><span class="special">();</span>
    437. 

  437.         <span class="keyword">int</span> <span class="identifier">z</span> <span class="special">=</span> <span class="identifier">Double2Int</span><span class="special">::</span><span class="identifier">convert</span><span class="special">(</span><span class="identifier">m</span><span class="special">);</span> <span class="comment">// By default throws positive_overflow()</span>
    438. 

  438.     <span class="special">}</span>
    439. 

  439.     <span class="keyword">catch</span> <span class="special">(</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">numeric</span><span class="special">::</span><span class="identifier">positive_overflow</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="special">)</span>
    440. 

  440.     <span class="special">{</span>
    441. 

  441.     <span class="special">}</span>
    442. 

  442. 

  443.     <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
    444. 

  444. <span class="special">}</span>
    445. 

  445. </pre>
    446. 

  446. </div>
    447. 

  447. </div>
    448. 

  448. <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
    449. 

  449. <td align="left"></td>
    450. 

  450. <td align="right"><div class="copyright-footer">Copyright &#169; 2004-2007 Fernando
    451. 

  451.       Luis Cacciola Carballal<p>
    452. 

  452.         Distributed under the Boost Software License, Version 1.0. (See accompanying
    453. 

  453.         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>)
    454. 

  454.       </p>
    455. 

  455. </div></td>
    456. 

  456. </tr></table>
    457. 

  457. <hr>
    458. 

  458. <div class="spirit-nav">
    459. 

  459. <a accesskey="p" href="definitions.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="type_requirements_and_user_defined_types_support.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
    460. 

  460. </div>
    461. 

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    462. 

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    463.