ceph/src/boost/libs/property_map/doc/LvaluePropertyMap.html

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   9 <Head>
  10 <Title>LvaluePropertyMap</Title>
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  18 <H2><A NAME="concept:LvaluePropertyMap"></A>
  19 LvaluePropertyMap
  20 </H2>
  21
  22 The LvaluePropertyMap provides <code>operator[]</code> and function <code>get()</code> for accessing a
  23 reference to a value object. The return type  refines that of function <code>get()</code>in <a
  24 href="./ReadablePropertyMap.html">ReadablePropertyMap</a>; it can only be a reference (for a <I>mutable</I> LvaluePropertyMap) or a const reference (for a <I>non-mutable</I> LvaluePropertyMap).
  25
  26 <H3>Refinement of</H3>
  27
  28 <a href="./ReadablePropertyMap.html">ReadablePropertyMap</a>
  29 for non-mutable or <a href="./ReadWritePropertyMap.html">ReadWritePropertyMap</a> for mutable property map.
  30
  31 <h3>Notation</h3>
  32
  33 <Table>
  34 <TR>
  35 <TD><tt>PMap</tt></TD>
  36 <TD>A type that is a model of LvaluePropertyMap.</TD>
  37 </TR>
  38 <TR>
  39 <TD><tt>pmap</tt></TD>
  40 <TD>An object of type <tt>PMap</tt>.</td>
  41 </TR>
  42 <TR>
  43 <TD><tt>key</tt></TD>
  44 <TD>An object of type <tt>boost::property_traits&lt;PMap&gt;::key_type</tt>.</td>
  45 </TR>
  46
  47 </table>
  48
  49
  50 <h3>Associated Types</h3>
  51
  52 <table border>
  53
  54 <tr>
  55 <td>Reference Type</td>
  56 <td><TT>boost::property_traits&lt;PMap&gt;::reference</TT></td>
  57 <td>
  58 The reference type, which must be a reference or const reference to
  59 the value type of the property map.
  60 </td>
  61 </tr>
  62
  63 <tr>
  64 <td>Property Map Category
  65 <td><TT>boost::property_traits&lt;PMap&gt;::category</TT></td>
  66 <td>
  67 The category of the property: a type convertible to
  68 <TT>boost::lvalue_property_map_tag</TT>.
  69 </td>
  70 </tr>
  71
  72 </table>
  73
  74 <h3>Valid Expressions</h3>
  75
  76 <table border>
  77 <tr>
  78 <th>Name</th><th>Expression</th><th>Return Type</th><th>Description</th>
  79 </tr>
  80
  81
  82 <tr>
  83 <td>Access Property Value </td>
  84 <TD><TT>pmap[key]</TT></TD>
  85 <TD>
  86 <TT>value_type&amp;</TT> for mutable, <TT>const value_type&amp;</TT>
  87 otherwise.
  88 </TD>
  89 <TD>Obtain a reference to the value associated with <TT>key</TT>.</TD>
  90 </TR>
  91 </TABLE>
  92
  93 <h3>Concept Checking Class</h3>
  94
  95 <pre>  template &lt;class PMap, class Key&gt;
  96   struct LvaluePropertyMapConcept
  97   {
  98     typedef typename property_traits&lt;PMap&gt;::category Category;
  99     typedef boost::lvalue_property_map_tag LvalueTag;
 100     typedef const typename property_traits&lt;PMap&gt;::value_type&amp; const_reference;
 101     void constraints() {
 102       function_requires&lt; ReadWritePropertyMapConcept&lt;PMap, Key&gt; &gt;();
 103       function_requires&lt; ConvertibleConcept&lt;Category, LvalueTag&gt; &gt;();
 104
 105       const_reference ref = pmap[k];
 106     }
 107     PMap pmap;
 108     Key k;
 109   };
 110
 111   template &lt;class PMap, class Key&gt;
 112   struct Mutable_LvaluePropertyMapConcept
 113   {
 114     typedef typename property_traits&lt;PMap&gt;::category Category;
 115     typedef boost::lvalue_property_map_tag LvalueTag;
 116     typedef typename property_traits&lt;PMap&gt;::value_type&amp; reference;
 117     void constraints() {
 118       function_requires&lt; ReadWritePropertyMapConcept&lt;PMap, Key&gt; &gt;();
 119       function_requires&lt;ConvertibleConcept&lt;Category, LvalueTag&gt; &gt;();
 120
 121       reference ref = pmap[k];
 122     }
 123     PMap pmap;
 124     Key k;
 125   };</pre>
 126
 127 <h3>See Also</h3>
 128
 129 <a href="./property_map.html">Property map concepts</a>
 130
 131
 132 <br>
 133 <HR>
 134 <TABLE>
 135 <TR valign=top>
 136 <TD nowrap>Copyright &copy 2000</TD><TD>
 137 <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>)
 138 </TD></TR></TABLE>
 139
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