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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="boost_asio.reference.TimeTraits"></a><a class="link" href="TimeTraits.html" title="Time traits requirements">Time traits requirements</a>
  28 </h3></div></div></div>
  29 <p>
  30         In the table below, <code class="computeroutput"><span class="identifier">X</span></code> denotes
  31         a time traits class for time type <code class="computeroutput"><span class="identifier">Time</span></code>,
  32         <code class="computeroutput"><span class="identifier">t</span></code>, <code class="computeroutput"><span class="identifier">t1</span></code>,
  33         and <code class="computeroutput"><span class="identifier">t2</span></code> denote values of type
  34         <code class="computeroutput"><span class="identifier">Time</span></code>, and <code class="computeroutput"><span class="identifier">d</span></code>
  35         denotes a value of type <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">duration_type</span></code>.
  36       </p>
  37 <div class="table">
  38 <a name="boost_asio.reference.TimeTraits.t0"></a><p class="title"><b>Table&#160;38.&#160;TimeTraits requirements</b></p>
  39 <div class="table-contents"><table class="table" summary="TimeTraits requirements">
  40 <colgroup>
  41 <col>
  42 <col>
  43 <col>
  44 </colgroup>
  45 <thead><tr>
  46 <th>
  47                 <p>
  48                   expression
  49                 </p>
  50               </th>
  51 <th>
  52                 <p>
  53                   return type
  54                 </p>
  55               </th>
  56 <th>
  57                 <p>
  58                   assertion/note<br> pre/post-condition
  59                 </p>
  60               </th>
  61 </tr></thead>
  62 <tbody>
  63 <tr>
  64 <td>
  65                 <p>
  66                   <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">time_type</span></code>
  67                 </p>
  68               </td>
  69 <td>
  70                 <p>
  71                   <code class="computeroutput"><span class="identifier">Time</span></code>
  72                 </p>
  73               </td>
  74 <td>
  75                 <p>
  76                   Represents an absolute time. Must support default construction,
  77                   and meet the requirements for <code class="computeroutput"><span class="identifier">CopyConstructible</span></code>
  78                   and <code class="computeroutput"><span class="identifier">Assignable</span></code>.
  79                 </p>
  80               </td>
  81 </tr>
  82 <tr>
  83 <td>
  84                 <p>
  85                   <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">duration_type</span></code>
  86                 </p>
  87               </td>
  88 <td>
  89               </td>
  90 <td>
  91                 <p>
  92                   Represents the difference between two absolute times. Must support
  93                   default construction, and meet the requirements for <code class="computeroutput"><span class="identifier">CopyConstructible</span></code> and <code class="computeroutput"><span class="identifier">Assignable</span></code>. A duration can be
  94                   positive, negative, or zero.
  95                 </p>
  96               </td>
  97 </tr>
  98 <tr>
  99 <td>
 100                 <p>
 101                   <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span></code>
 102                 </p>
 103               </td>
 104 <td>
 105                 <p>
 106                   <code class="computeroutput"><span class="identifier">time_type</span></code>
 107                 </p>
 108               </td>
 109 <td>
 110                 <p>
 111                   Returns the current time.
 112                 </p>
 113               </td>
 114 </tr>
 115 <tr>
 116 <td>
 117                 <p>
 118                   <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">add</span><span class="special">(</span><span class="identifier">t</span><span class="special">,</span>
 119                   <span class="identifier">d</span><span class="special">);</span></code>
 120                 </p>
 121               </td>
 122 <td>
 123                 <p>
 124                   <code class="computeroutput"><span class="identifier">time_type</span></code>
 125                 </p>
 126               </td>
 127 <td>
 128                 <p>
 129                   Returns a new absolute time resulting from adding the duration
 130                   <code class="computeroutput"><span class="identifier">d</span></code> to the absolute
 131                   time <code class="computeroutput"><span class="identifier">t</span></code>.
 132                 </p>
 133               </td>
 134 </tr>
 135 <tr>
 136 <td>
 137                 <p>
 138                   <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">subtract</span><span class="special">(</span><span class="identifier">t1</span><span class="special">,</span>
 139                   <span class="identifier">t2</span><span class="special">);</span></code>
 140                 </p>
 141               </td>
 142 <td>
 143                 <p>
 144                   <code class="computeroutput"><span class="identifier">duration_type</span></code>
 145                 </p>
 146               </td>
 147 <td>
 148                 <p>
 149                   Returns the duration resulting from subtracting <code class="computeroutput"><span class="identifier">t2</span></code>
 150                   from <code class="computeroutput"><span class="identifier">t1</span></code>.
 151                 </p>
 152               </td>
 153 </tr>
 154 <tr>
 155 <td>
 156                 <p>
 157                   <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">less_than</span><span class="special">(</span><span class="identifier">t1</span><span class="special">,</span>
 158                   <span class="identifier">t2</span><span class="special">);</span></code>
 159                 </p>
 160               </td>
 161 <td>
 162                 <p>
 163                   <code class="computeroutput"><span class="keyword">bool</span></code>
 164                 </p>
 165               </td>
 166 <td>
 167                 <p>
 168                   Returns whether <code class="computeroutput"><span class="identifier">t1</span></code>
 169                   is to be treated as less than <code class="computeroutput"><span class="identifier">t2</span></code>.
 170                 </p>
 171               </td>
 172 </tr>
 173 <tr>
 174 <td>
 175                 <p>
 176                   <code class="computeroutput"><span class="identifier">X</span><span class="special">::</span><span class="identifier">to_posix_duration</span><span class="special">(</span><span class="identifier">d</span><span class="special">);</span></code>
 177                 </p>
 178               </td>
 179 <td>
 180                 <p>
 181                   <code class="computeroutput"><span class="identifier">date_time</span><span class="special">::</span><span class="identifier">time_duration_type</span></code>
 182                 </p>
 183               </td>
 184 <td>
 185                 <p>
 186                   Returns the <code class="computeroutput"><span class="identifier">date_time</span><span class="special">::</span><span class="identifier">time_duration_type</span></code>
 187                   value that most closely represents the duration <code class="computeroutput"><span class="identifier">d</span></code>.
 188                 </p>
 189               </td>
 190 </tr>
 191 </tbody>
 192 </table></div>
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