[ceph.git] / ceph / src / boost / libs / property_map / doc / LvaluePropertyMap.html

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<Title>LvaluePropertyMap</Title>
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<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&lt;PMap&gt;::key_type</tt>.</td>
</TR>

</table>


<h3>Associated Types</h3>

<table border>

<tr>
<td>Reference Type</td>
<td><TT>boost::property_traits&lt;PMap&gt;::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&lt;PMap&gt;::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&amp;</TT> for mutable, <TT>const value_type&amp;</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 &lt;class PMap, class Key&gt;
  struct LvaluePropertyMapConcept
  {
    typedef typename property_traits&lt;PMap&gt;::category Category;
    typedef boost::lvalue_property_map_tag LvalueTag;
    typedef const typename property_traits&lt;PMap&gt;::value_type&amp; const_reference;
    void constraints() {
      function_requires&lt; ReadWritePropertyMapConcept&lt;PMap, Key&gt; &gt;();
      function_requires&lt; ConvertibleConcept&lt;Category, LvalueTag&gt; &gt;();

      const_reference ref = pmap[k];
    }
    PMap pmap;
    Key k;
  };

  template &lt;class PMap, class Key&gt;
  struct Mutable_LvaluePropertyMapConcept
  {
    typedef typename property_traits&lt;PMap&gt;::category Category;
    typedef boost::lvalue_property_map_tag LvalueTag;
    typedef typename property_traits&lt;PMap&gt;::value_type&amp; reference;
    void constraints() { 
      function_requires&lt; ReadWritePropertyMapConcept&lt;PMap, Key&gt; &gt;();
      function_requires&lt;ConvertibleConcept&lt;Category, LvalueTag&gt; &gt;();

      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 &copy 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>)
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	2	<!--
	3	Copyright (c) Jeremy Siek 2000
	4
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	6	(See accompanying file LICENSE_1_0.txt or copy at
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	9	<Head>
	10	<Title>LvaluePropertyMap</Title>
	11	<BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b"
	12	ALINK="#ff0000">
	13	<IMG SRC="../../../boost.png"
	14	ALT="C++ Boost" width="277" height="86">
	15
	16	<BR Clear>
	17
	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<PMap>::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<PMap>::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<PMap>::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&</TT> for mutable, <TT>const value_type&</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 <class PMap, class Key>
96	struct LvaluePropertyMapConcept
97	{
98	typedef typename property_traits<PMap>::category Category;
99	typedef boost::lvalue_property_map_tag LvalueTag;
100	typedef const typename property_traits<PMap>::value_type& const_reference;
101	void constraints() {
102	function_requires< ReadWritePropertyMapConcept<PMap, Key> >();
103	function_requires< ConvertibleConcept<Category, LvalueTag> >();
104
105	const_reference ref = pmap[k];
106	}
107	PMap pmap;
108	Key k;
109	};
110
111	template <class PMap, class Key>
112	struct Mutable_LvaluePropertyMapConcept
113	{
114	typedef typename property_traits<PMap>::category Category;
115	typedef boost::lvalue_property_map_tag LvalueTag;
116	typedef typename property_traits<PMap>::value_type& reference;
117	void constraints() {
118	function_requires< ReadWritePropertyMapConcept<PMap, Key> >();
119	function_requires<ConvertibleConcept<Category, LvalueTag> >();
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
140	</BODY>
141	</HTML>