/Src/Dependencies/Boost/libs/property_map/doc/LvaluePropertyMap.html

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  3.      Copyright (c) Jeremy Siek 2000
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  9. <Head>
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  10. <Title>LvaluePropertyMap</Title>
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  17. 

  18. <H2><A NAME="concept:LvaluePropertyMap"></A>
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  19. LvaluePropertyMap
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  20. </H2>
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  21. 

  22. The LvaluePropertyMap provides an interface for accessing a
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  23. reference to a property object (instead of a copy of the object as in
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  24. the <TT>get()</TT> function required by <a
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  25. href="./ReadablePropertyMap.html">ReadablePropertyMap</a>). An
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  26. LvaluePropertyMap can be <I>mutable</I> or
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  27. <I>non-mutable</I>. The mutable LvaluePropertyMap returns a
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  28. reference whereas the non-mutable returns a const reference.
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  29. 

  30. <H3>Refinement of</H3>
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  31. 

  32. <a href="./ReadablePropertyMap.html">ReadablePropertyMap</a>
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  33. for non-mutable or <a href="./ReadWritePropertyMap.html">ReadWritePropertyMap</a> for mutable property map.
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  34. 

  35. <h3>Notation</h3>
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  36. 

  37. <Table>
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  38. <TR>
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  39. <TD><tt>PMap</tt></TD>
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  40. <TD>A type that is a model of LvaluePropertyMap.</TD>
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  41. </TR>
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  42. <TR>
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  43. <TD><tt>pmap</tt></TD>
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  44. <TD>An object of type <tt>PMap</tt>.</td>
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  45. </TR>
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  46. <TR>
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  47. <TD><tt>key</tt></TD>
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  48. <TD>An object of type <tt>boost::property_traits&lt;PMap&gt;::key_type</tt>.</td>
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  49. </TR>
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  50. 

  51. </table>
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  52. 

  53. 

  54. <h3>Associated Types</h3>
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  55. 

  56. <table border>
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  57. 

  58. <tr>
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  59. <td>Reference Type</td>
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  60. <td><TT>boost::property_traits&lt;PMap&gt;::reference</TT></td> 
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  61. <td>
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  62. The reference type, which must be a reference or const reference to
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  63. the value typeof the property map.
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  64. </td>
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  65. </tr>
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  66. 

  67. <tr>
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  68. <td>Property Map Category 
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  69. <td><TT>boost::property_traits&lt;PMap&gt;::category</TT></td> 
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  70. <td>
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  71. The category of the property: a type convertible to
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  72. <TT>boost::lvalue_property_map_tag</TT>.
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  73. </td>
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  74. </tr>
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  75. 

  76. </table>
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  77. 

  78. <h3>Valid Expressions</h3>
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  79. 

  80. <table border>
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  81. <tr>
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  82. <th>Name</th><th>Expression</th><th>Return Type</th><th>Description</th>
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  83. </tr>
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  84. 

  85. 

  86. <tr>
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  87. <td>Access Property Value </td>
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  88. <TD><TT>pmap[key]</TT></TD>
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  89. <TD>
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  90. <TT>value_type&amp;</TT> for mutable, <TT>const value_type&amp;</TT>
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  91. otherwise.
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  92. </TD>
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  93. <TD>Obtain a reference to the property identified by <TT>key</TT>.</TD>
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  94. </TR>
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  95. </TABLE>
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  96. 

  97. <h3>Concept Checking Class</h3>
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  98. 

  99. <pre>  template &lt;class PMap, class Key&gt;
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  100.   struct LvaluePropertyMapConcept
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  101.   {
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  102.     typedef typename property_traits&lt;PMap&gt;::category Category;
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  103.     typedef boost::lvalue_property_map_tag LvalueTag;
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  104.     typedef const typename property_traits&lt;PMap&gt;::value_type&amp; const_reference;
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  105.     void constraints() {
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  106.       function_requires&lt; ReadWritePropertyMapConcept&lt;PMap, Key&gt; &gt;();
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  107.       function_requires&lt; ConvertibleConcept&lt;Category, LvalueTag&gt; &gt;();
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  108. 

  109.       const_reference ref = pmap[k];
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  110.     }
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  111.     PMap pmap;
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  112.     Key k;
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  113.   };
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  114. 

  115.   template &lt;class PMap, class Key&gt;
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  116.   struct Mutable_LvaluePropertyMapConcept
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  117.   {
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  118.     typedef typename property_traits&lt;PMap&gt;::category Category;
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  119.     typedef boost::lvalue_property_map_tag LvalueTag;
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  120.     typedef typename property_traits&lt;PMap&gt;::value_type&amp; reference;
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  121.     void constraints() { 
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  122.       function_requires&lt; ReadWritePropertyMapConcept&lt;PMap, Key&gt; &gt;();
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  123.       function_requires&lt;ConvertibleConcept&lt;Category, LvalueTag&gt; &gt;();
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  124. 

  125.       reference ref = pmap[k];
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  126.     }
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  127.     PMap pmap;
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  128.     Key k;
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  129.   };</pre>
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  130. 

  131. <h3>See Also</h3>
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  132. 

  133. <a href="./property_map.html">Property map concepts</a>
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  136. <br>
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  137. <HR>
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  138. <TABLE>
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  139. <TR valign=top>
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  140. <TD nowrap>Copyright &copy 2000</TD><TD>
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  141. <a HREF="http://www.boost.org/people/jeremy_siek.htm">Jeremy Siek</a>, Univ.of Notre Dame (<A HREF="mailto:jsiek@lsc.nd.edu">jsiek@lsc.nd.edu</A>)
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  142. </TD></TR></TABLE>
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