1<?xml version="1.0" ?> 2<!-- 3 Copyright 2010 Eric Niebler 4 5 Distributed under the Boost 6 Software License, Version 1.0. (See accompanying 7 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 8 --> 9<concept name="Expr" category="utility"> 10 <param name="Expr" role="expession-type"/> 11 <param name="Tag" role="tag-type"/> 12 <param name="Domain" role="domain-type"/> 13 <param name="N" role="mpl-integral-constant-type"/> 14 15 <models-sentence> 16 The type <arg num="1"/> must be a model of <self/>. 17 </models-sentence> 18 19 <models-sentence> 20 The type <arg num="3"/> must be a model of <conceptname>Domain</conceptname>. 21 </models-sentence> 22 23 <models-sentence> 24 The type <arg num="4"/> must be a model of MPL Integral Constant. 25 </models-sentence> 26 27 <description> 28 <para> 29 An Expr represents a tagged node in an expression tree. 30 The children of the Expr must themselves satisfy the 31 Expr concept. The Expr has an arity representing the 32 number of children. If the number of children is zero, 33 the Expr also has a value. An Expr also has an associated 34 <conceptname>Domain</conceptname>. 35 </para> 36 </description> 37 38 <notation variables="e"> 39 <sample-value> 40 <type name="Expr"/> 41 </sample-value> 42 </notation> 43 44 <associated-type name="proto_tag"> 45 <get-member-type name="proto_tag"> 46 <type name="Expr"/> 47 </get-member-type> 48 <description> 49 <simpara>The tag type of the Expr.</simpara> 50 </description> 51 </associated-type> 52 53 <associated-type name="proto_args"> 54 <get-member-type name="proto_args"> 55 <type name="Expr"/> 56 </get-member-type> 57 <description> 58 <simpara>A typelist representing either the types of the child nodes, or, 59 if the arity of the Expr is 0, of the value of the terminal.</simpara> 60 </description> 61 </associated-type> 62 63 <associated-type name="proto_arity"> 64 <get-member-type name="proto_arity"> 65 <type name="Expr"/> 66 </get-member-type> 67 <description> 68 <simpara> 69 The arity (number of child nodes) of the Expr. 70 <computeroutput>proto_arity</computeroutput> is an MPL Integral Constant. 71 </simpara> 72 </description> 73 </associated-type> 74 75 <associated-type name="proto_grammar"> 76 <get-member-type name="proto_grammar"> 77 <type name="Expr"/> 78 </get-member-type> 79 <description> 80 <simpara> 81 A typedef for an instantiation of 82 <classname alt="boost::proto::basic_expr"> 83 <code>proto::basic_expr<></code> 84 </classname> 85 that is equivalent to Expr. Expression types are equivalent if they have the 86 same <code>proto_tag</code>, <code>proto_args</code>, and <code>proto_arity</code>. 87 </simpara> 88 </description> 89 </associated-type> 90 91 <associated-type name="proto_base_expr"> 92 <get-member-type name="proto_base_expr"> 93 <type name="Expr"/> 94 </get-member-type> 95 <description> 96 <simpara> 97 A typedef for an instantiation of 98 <classname alt="boost::proto::expr"><code>proto::expr<></code></classname> or 99 <classname alt="boost::proto::basic_expr"><code>proto::basic_expr<></code></classname> 100 that is equivalent to Expr. Expression types are equivalent if they have the 101 same <code>proto_tag</code>, <code>proto_args</code>, and <code>proto_arity</code>. 102 </simpara> 103 </description> 104 </associated-type> 105 106 <associated-type name="proto_derived_expr"> 107 <get-member-type name="proto_derived_expr"> 108 <type name="Expr"/> 109 </get-member-type> 110 <description> 111 <simpara> 112 A typedef for <code>Expr</code>. 113 </simpara> 114 </description> 115 </associated-type> 116 117 <associated-type name="proto_domain"> 118 <get-member-type name="proto_domain"> 119 <type name="Expr"/> 120 </get-member-type> 121 <description> 122 <simpara> 123 The Domain of the Expr. <computeroutput>proto_domain</computeroutput> 124 models <conceptname>Domain</conceptname>. 125 </simpara> 126 </description> 127 </associated-type> 128 129 <associated-type name="proto_childN"> 130 <get-member-type name="proto_childN"> 131 <type name="Expr"/> 132 </get-member-type> 133 <description> 134 <simpara>The type of the Nth child of Expr. Requires 135 <code>0 == N::value || N::value < proto_arity::value</code></simpara> 136 </description> 137 </associated-type> 138 139 <valid-expression name="Get N-th Child"> 140 <apply-function name="boost::proto::child< N >"> 141 <sample-value> 142 <type name="Expr"/> 143 </sample-value> 144 </apply-function> 145 <return-type> 146 <require-same-type testable="yes"> 147 <type name="proto_childN"/> 148 </require-same-type> 149 </return-type> 150 <semantics>Extracts the Nth child from this Expr. 151 Requires <computeroutput>N::value < proto_arity::value</computeroutput>.</semantics> 152 </valid-expression> 153 154 <valid-expression name="Get Terminal Value"> 155 <apply-function name="boost::proto::value"> 156 <sample-value> 157 <type name="Expr"/> 158 </sample-value> 159 </apply-function> 160 <return-type> 161 <require-same-type testable="yes"> 162 <type name="proto_child0"/> 163 </require-same-type> 164 </return-type> 165 <semantics> 166 Extracts the value from a terminal Expr. 167 Requires <computeroutput>0 == proto_arity::value</computeroutput>. 168 </semantics> 169 </valid-expression> 170 171 <valid-expression name="Get Base"> 172 <apply-method name="proto_base"> 173 <sample-value> 174 <type name="Expr"/> 175 </sample-value> 176 </apply-method> 177 <return-type> 178 <require-same-type testable="yes"> 179 <type name="proto_base_expr"/> 180 </require-same-type> 181 </return-type> 182 <semantics> 183 Returns an object of type 184 <classname alt="boost::proto::expr"><code>proto::expr<></code></classname> or 185 <classname alt="boost::proto::basic_expr"><code>proto::basic_expr<></code></classname> 186 that is equivalent to <code>e</code>. 187 </semantics> 188 </valid-expression> 189 190 <example-model> 191 <type name="boost::proto::literal< int >"/> 192 </example-model> 193 194</concept> 195