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- Copyright (c) Jeremy Siek 2000
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- <Head>
- <Title>LvaluePropertyMap</Title>
- <BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b"
- ALINK="#ff0000">
- <IMG SRC="../../../boost.png"
- ALT="C++ Boost" width="277" height="86">
- <BR Clear>
- <H2><A NAME="concept:LvaluePropertyMap"></A>
- LvaluePropertyMap
- </H2>
- The LvaluePropertyMap provides <code>operator[]</code> and function <code>get()</code> for accessing a
- reference to a value object. The return type refines that of function <code>get()</code>in <a
- 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).
- <H3>Refinement of</H3>
- <a href="./ReadablePropertyMap.html">ReadablePropertyMap</a>
- for non-mutable or <a href="./ReadWritePropertyMap.html">ReadWritePropertyMap</a> for mutable property map.
- <h3>Notation</h3>
- <Table>
- <TR>
- <TD><tt>PMap</tt></TD>
- <TD>A type that is a model of LvaluePropertyMap.</TD>
- </TR>
- <TR>
- <TD><tt>pmap</tt></TD>
- <TD>An object of type <tt>PMap</tt>.</td>
- </TR>
- <TR>
- <TD><tt>key</tt></TD>
- <TD>An object of type <tt>boost::property_traits<PMap>::key_type</tt>.</td>
- </TR>
- </table>
- <h3>Associated Types</h3>
- <table border>
- <tr>
- <td>Reference Type</td>
- <td><TT>boost::property_traits<PMap>::reference</TT></td>
- <td>
- The reference type, which must be a reference or const reference to
- the value type of the property map.
- </td>
- </tr>
- <tr>
- <td>Property Map Category
- <td><TT>boost::property_traits<PMap>::category</TT></td>
- <td>
- The category of the property: a type convertible to
- <TT>boost::lvalue_property_map_tag</TT>.
- </td>
- </tr>
- </table>
- <h3>Valid Expressions</h3>
- <table border>
- <tr>
- <th>Name</th><th>Expression</th><th>Return Type</th><th>Description</th>
- </tr>
- <tr>
- <td>Access Property Value </td>
- <TD><TT>pmap[key]</TT></TD>
- <TD>
- <TT>value_type&</TT> for mutable, <TT>const value_type&</TT>
- otherwise.
- </TD>
- <TD>Obtain a reference to the value associated with <TT>key</TT>.</TD>
- </TR>
- </TABLE>
- <h3>Concept Checking Class</h3>
- <pre> template <class PMap, class Key>
- struct LvaluePropertyMapConcept
- {
- typedef typename property_traits<PMap>::category Category;
- typedef boost::lvalue_property_map_tag LvalueTag;
- typedef const typename property_traits<PMap>::value_type& const_reference;
- void constraints() {
- function_requires< ReadWritePropertyMapConcept<PMap, Key> >();
- function_requires< ConvertibleConcept<Category, LvalueTag> >();
- const_reference ref = pmap[k];
- }
- PMap pmap;
- Key k;
- };
- template <class PMap, class Key>
- struct Mutable_LvaluePropertyMapConcept
- {
- typedef typename property_traits<PMap>::category Category;
- typedef boost::lvalue_property_map_tag LvalueTag;
- typedef typename property_traits<PMap>::value_type& reference;
- void constraints() {
- function_requires< ReadWritePropertyMapConcept<PMap, Key> >();
- function_requires<ConvertibleConcept<Category, LvalueTag> >();
- reference ref = pmap[k];
- }
- PMap pmap;
- Key k;
- };</pre>
- <h3>See Also</h3>
- <a href="./property_map.html">Property map concepts</a>
- <br>
- <HR>
- <TABLE>
- <TR valign=top>
- <TD nowrap>Copyright © 2000</TD><TD>
- <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>)
- </TD></TR></TABLE>
- </BODY>
- </HTML>
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