cpp_type_traits.h

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00001 // The -*- C++ -*- type traits classes for internal use in libstdc++ 00002 00003 // Copyright (C) 2000, 2001 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the 00007 // terms of the GNU General Public License as published by the 00008 // Free Software Foundation; either version 2, or (at your option) 00009 // any later version. 00010 00011 // This library is distributed in the hope that it will be useful, 00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00014 // GNU General Public License for more details. 00015 00016 // You should have received a copy of the GNU General Public License along 00017 // with this library; see the file COPYING. If not, write to the Free 00018 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, 00019 // USA. 00020 00021 // As a special exception, you may use this file as part of a free software 00022 // library without restriction. Specifically, if other files instantiate 00023 // templates or use macros or inline functions from this file, or you compile 00024 // this file and link it with other files to produce an executable, this 00025 // file does not by itself cause the resulting executable to be covered by 00026 // the GNU General Public License. This exception does not however 00027 // invalidate any other reasons why the executable file might be covered by 00028 // the GNU General Public License. 00029 00030 // Written by Gabriel Dos Reis <dosreis@cmla.ens-cachan.fr> 00031 00037 #ifndef _CPP_BITS_CPP_TYPE_TRAITS_H 00038 #define _CPP_BITS_CPP_TYPE_TRAITS_H 1 00039 00040 #pragma GCC system_header 00041 00042 // 00043 // This file provides some compile-time information about various types. 00044 // These representations were designed, on purpose, to be constant-expressions 00045 // and not types as found in <stl/bits/type_traits.h>. In particular, they 00046 // can be used in control structures and the optimizer hopefully will do 00047 // the obvious thing. 00048 // 00049 // Why integral expressions, and not functions nor types? 00050 // Firstly, these compile-time entities are used as template-arguments 00051 // so function return values won't work: We need compile-time entities. 00052 // We're left with types and constant integral expressions. 00053 // Secondly, from the point of view of ease of use, type-based compile-time 00054 // information is -not- *that* convenient. On has to write lots of 00055 // overloaded functions and to hope that the compiler will select the right 00056 // one. As a net effect, the overall structure isn't very clear at first 00057 // glance. 00058 // Thirdly, partial ordering and overload resolution (of function templates) 00059 // is highly costly in terms of compiler-resource. It is a Good Thing to 00060 // keep these resource consumption as least as possible. 00061 // 00062 // See valarray_array.h for a case use. 00063 // 00064 // -- Gaby (dosreis@cmla.ens-cachan.fr) 2000-03-06. 00065 // 00066 00067 namespace std 00068 { 00069 template<typename _Tp> 00070 struct __is_void 00071 { 00072 enum 00073 { 00074 _M_type = 0 00075 }; 00076 }; 00077 00078 template<> 00079 struct __is_void<void> 00080 { 00081 enum 00082 { 00083 _M_type = 1 00084 }; 00085 }; 00086 00087 // 00088 // Integer types 00089 // 00090 template<typename _Tp> 00091 struct __is_integer 00092 { 00093 enum 00094 { 00095 _M_type = 0 00096 }; 00097 }; 00098 00099 // Thirteen specializations (yes there are eleven standard integer 00100 // types; 'long long' and 'unsigned long long' are supported as 00101 // extensions) 00102 template<> 00103 struct __is_integer<bool> 00104 { 00105 enum 00106 { 00107 _M_type = 1 00108 }; 00109 }; 00110 00111 template<> 00112 struct __is_integer<char> 00113 { 00114 enum 00115 { 00116 _M_type = 1 00117 }; 00118 }; 00119 00120 template<> 00121 struct __is_integer<signed char> 00122 { 00123 enum 00124 { 00125 _M_type = 1 00126 }; 00127 }; 00128 00129 template<> 00130 struct __is_integer<unsigned char> 00131 { 00132 enum 00133 { 00134 _M_type = 1 00135 }; 00136 }; 00137 00138 # ifdef _GLIBCPP_USE_WCHAR_T 00139 template<> 00140 struct __is_integer<wchar_t> 00141 { 00142 enum 00143 { 00144 _M_type = 1 00145 }; 00146 }; 00147 # endif 00148 00149 template<> 00150 struct __is_integer<short> 00151 { 00152 enum 00153 { 00154 _M_type = 1 00155 }; 00156 }; 00157 00158 template<> 00159 struct __is_integer<unsigned short> 00160 { 00161 enum 00162 { 00163 _M_type = 1 00164 }; 00165 }; 00166 00167 template<> 00168 struct __is_integer<int> 00169 { 00170 enum 00171 { 00172 _M_type = 1 00173 }; 00174 }; 00175 00176 template<> 00177 struct __is_integer<unsigned int> 00178 { 00179 enum 00180 { 00181 _M_type = 1 00182 }; 00183 }; 00184 00185 template<> 00186 struct __is_integer<long> 00187 { 00188 enum 00189 { 00190 _M_type = 1 00191 }; 00192 }; 00193 00194 template<> 00195 struct __is_integer<unsigned long> 00196 { 00197 enum 00198 { 00199 _M_type = 1 00200 }; 00201 }; 00202 00203 template<> 00204 struct __is_integer<long long> 00205 { 00206 enum 00207 { 00208 _M_type = 1 00209 }; 00210 }; 00211 00212 template<> 00213 struct __is_integer<unsigned long long> 00214 { 00215 enum 00216 { 00217 _M_type = 1 00218 }; 00219 }; 00220 00221 // 00222 // Floating point types 00223 // 00224 template<typename _Tp> 00225 struct __is_floating 00226 { 00227 enum 00228 { 00229 _M_type = 0 00230 }; 00231 }; 00232 00233 // three specializations (float, double and 'long double') 00234 template<> 00235 struct __is_floating<float> 00236 { 00237 enum 00238 { 00239 _M_type = 1 00240 }; 00241 }; 00242 00243 template<> 00244 struct __is_floating<double> 00245 { 00246 enum 00247 { 00248 _M_type = 1 00249 }; 00250 }; 00251 00252 template<> 00253 struct __is_floating<long double> 00254 { 00255 enum 00256 { 00257 _M_type = 1 00258 }; 00259 }; 00260 00261 // 00262 // An arithmetic type is an integer type or a floating point type 00263 // 00264 template<typename _Tp> 00265 struct __is_arithmetic 00266 { 00267 enum 00268 { 00269 _M_type = __is_integer<_Tp>::_M_type || __is_floating<_Tp>::_M_type 00270 }; 00271 }; 00272 00273 // 00274 // A fundamental type is `void' or and arithmetic type 00275 // 00276 template<typename _Tp> 00277 struct __is_fundamental 00278 { 00279 enum 00280 { 00281 _M_type = __is_void<_Tp>::_M_type || __is_arithmetic<_Tp>::_M_type 00282 }; 00283 }; 00284 00285 // 00286 // For the immediate use, the following is a good approximation 00287 // 00288 template<typename _Tp> 00289 struct __is_pod 00290 { 00291 enum 00292 { 00293 _M_type = __is_fundamental<_Tp>::_M_type 00294 }; 00295 }; 00296 00297 } // namespace std 00298 00299 00300 #endif //_CPP_BITS_CPP_TYPE_TRAITS_H

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