| [12] | 1 | <HTML> |
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| 2 | <!-- |
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| 3 | -- Copyright (c) Jeremy Siek 2000 |
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| 4 | -- |
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| 5 | -- Permission to use, copy, modify, distribute and sell this software |
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| 6 | -- and its documentation for any purpose is hereby granted without fee, |
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| 7 | -- provided that the above copyright notice appears in all copies and |
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| 8 | -- that both that copyright notice and this permission notice appear |
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| 9 | -- in supporting documentation. Silicon Graphics makes no |
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| 10 | -- representations about the suitability of this software for any |
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| 11 | -- purpose. It is provided "as is" without express or implied warranty. |
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| 12 | --> |
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| 13 | <Head> |
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| 14 | <Title>LvaluePropertyMap</Title> |
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| 15 | <BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" |
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| 16 | ALINK="#ff0000"> |
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| 17 | <IMG SRC="../../boost.png" |
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| 18 | ALT="C++ Boost" width="277" height="86"> |
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| 19 | |
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| 20 | <BR Clear> |
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| 21 | |
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| 22 | <H2><A NAME="concept:LvaluePropertyMap"></A> |
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| 23 | LvaluePropertyMap |
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| 24 | </H2> |
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| 25 | |
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| 26 | The LvaluePropertyMap provides an interface for accessing a |
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| 27 | reference to a property object (instead of a copy of the object as in |
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| 28 | the <TT>get()</TT> function required by <a |
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| 29 | href="./ReadablePropertyMap.html">ReadablePropertyMap</a>). An |
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| 30 | LvaluePropertyMap can be <I>mutable</I> or |
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| 31 | <I>non-mutable</I>. The mutable LvaluePropertyMap returns a |
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| 32 | reference whereas the non-mutable returns a const reference. |
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| 33 | |
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| 34 | <H3>Refinement of</H3> |
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| 35 | |
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| 36 | <a href="./ReadablePropertyMap.html">ReadablePropertyMap</a> |
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| 37 | for non-mutable or <a href="./ReadWritePropertyMap.html">ReadWritePropertyMap</a> for mutable property map. |
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| 38 | |
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| 39 | <h3>Notation</h3> |
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| 40 | |
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| 41 | <Table> |
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| 42 | <TR> |
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| 43 | <TD><tt>PMap</tt></TD> |
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| 44 | <TD>A type that is a model of LvaluePropertyMap.</TD> |
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| 45 | </TR> |
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| 46 | <TR> |
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| 47 | <TD><tt>pmap</tt></TD> |
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| 48 | <TD>An object of type <tt>PMap</tt>.</td> |
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| 49 | </TR> |
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| 50 | <TR> |
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| 51 | <TD><tt>key</tt></TD> |
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| 52 | <TD>An object of type <tt>boost::property_traits<PMap>::key_type</tt>.</td> |
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| 53 | </TR> |
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| 54 | |
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| 55 | </table> |
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| 56 | |
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| 57 | |
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| 58 | <h3>Associated Types</h3> |
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| 59 | |
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| 60 | <table border> |
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| 61 | |
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| 62 | <tr> |
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| 63 | <td>Reference Type</td> |
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| 64 | <td><TT>boost::property_traits<PMap>::reference</TT></td> |
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| 65 | <td> |
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| 66 | The reference type, which must be a reference or const reference to |
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| 67 | the value typeof the property map. |
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| 68 | </td> |
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| 69 | </tr> |
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| 70 | |
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| 71 | <tr> |
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| 72 | <td>Property Map Category |
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| 73 | <td><TT>boost::property_traits<PMap>::category</TT></td> |
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| 74 | <td> |
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| 75 | The category of the property: a type convertible to |
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| 76 | <TT>boost::lvalue_property_map_tag</TT>. |
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| 77 | </td> |
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| 78 | </tr> |
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| 79 | |
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| 80 | </table> |
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| 81 | |
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| 82 | <h3>Valid Expressions</h3> |
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| 83 | |
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| 84 | <table border> |
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| 85 | <tr> |
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| 86 | <th>Name</th><th>Expression</th><th>Return Type</th><th>Description</th> |
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| 87 | </tr> |
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| 88 | |
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| 89 | |
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| 90 | <tr> |
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| 91 | <td>Access Property Value </td> |
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| 92 | <TD><TT>pmap[key]</TT></TD> |
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| 93 | <TD> |
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| 94 | <TT>value_type&</TT> for mutable, <TT>const value_type&</TT> |
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| 95 | otherwise. |
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| 96 | </TD> |
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| 97 | <TD>Obtain a reference to the property identified by <TT>key</TT>.</TD> |
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| 98 | </TR> |
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| 99 | </TABLE> |
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| 100 | |
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| 101 | <h3>Concept Checking Class</h3> |
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| 102 | |
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| 103 | <pre> template <class PMap, class Key> |
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| 104 | struct LvaluePropertyMapConcept |
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| 105 | { |
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| 106 | typedef typename property_traits<PMap>::category Category; |
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| 107 | typedef boost::lvalue_property_map_tag LvalueTag; |
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| 108 | typedef const typename property_traits<PMap>::value_type& const_reference; |
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| 109 | void constraints() { |
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| 110 | function_requires< ReadWritePropertyMapConcept<PMap, Key> >(); |
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| 111 | function_requires< ConvertibleConcept<Category, LvalueTag> >(); |
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| 112 | |
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| 113 | const_reference ref = pmap[k]; |
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| 114 | } |
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| 115 | PMap pmap; |
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| 116 | Key k; |
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| 117 | }; |
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| 118 | |
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| 119 | template <class PMap, class Key> |
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| 120 | struct Mutable_LvaluePropertyMapConcept |
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| 121 | { |
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| 122 | typedef typename property_traits<PMap>::category Category; |
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| 123 | typedef boost::lvalue_property_map_tag LvalueTag; |
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| 124 | typedef typename property_traits<PMap>::value_type& reference; |
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| 125 | void constraints() { |
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| 126 | function_requires< ReadWritePropertyMapConcept<PMap, Key> >(); |
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| 127 | function_requires<ConvertibleConcept<Category, LvalueTag> >(); |
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| 128 | |
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| 129 | reference ref = pmap[k]; |
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| 130 | } |
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| 131 | PMap pmap; |
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| 132 | Key k; |
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| 133 | };</pre> |
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| 134 | |
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| 135 | <h3>See Also</h3> |
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| 136 | |
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| 137 | <a href="./property_map.html">Property map concepts</a> |
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| 138 | |
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| 139 | |
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| 140 | <br> |
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| 141 | <HR> |
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| 142 | <TABLE> |
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| 143 | <TR valign=top> |
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| 144 | <TD nowrap>Copyright © 2000</TD><TD> |
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| 145 | <a HREF="../../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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| 146 | </TD></TR></TABLE> |
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| 147 | |
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| 148 | </BODY> |
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| 149 | </HTML> |
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