libstdc++-v3/include/bits/cpp_type_traits.h

   1 // The  -*- C++ -*- type traits classes for internal use in libstdc++
   2
   3 // Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
   4 // Free Software Foundation, Inc.
   5 //
   6 // This file is part of the GNU ISO C++ Library.  This library is free
   7 // software; you can redistribute it and/or modify it under the
   8 // terms of the GNU General Public License as published by the
   9 // Free Software Foundation; either version 2, or (at your option)
  10 // any later version.
  11
  12 // This library is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16
  17 // You should have received a copy of the GNU General Public License along
  18 // with this library; see the file COPYING.  If not, write to the Free
  19 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  20 // USA.
  21
  22 // As a special exception, you may use this file as part of a free software
  23 // library without restriction.  Specifically, if other files instantiate
  24 // templates or use macros or inline functions from this file, or you compile
  25 // this file and link it with other files to produce an executable, this
  26 // file does not by itself cause the resulting executable to be covered by
  27 // the GNU General Public License.  This exception does not however
  28 // invalidate any other reasons why the executable file might be covered by
  29 // the GNU General Public License.
  30
  31 /** @file cpp_type_traits.h
  32  *  This is an internal header file, included by other library headers.
  33  *  You should not attempt to use it directly.
  34  */
  35
  36 // Written by Gabriel Dos Reis <dosreis@cmla.ens-cachan.fr>
  37
  38 #ifndef _CPP_TYPE_TRAITS_H
  39 #define _CPP_TYPE_TRAITS_H 1
  40
  41 #pragma GCC system_header
  42
  43 #include <bits/c++config.h>
  44
  45 //
  46 // This file provides some compile-time information about various types.
  47 // These representations were designed, on purpose, to be constant-expressions
  48 // and not types as found in <bits/type_traits.h>.  In particular, they
  49 // can be used in control structures and the optimizer hopefully will do
  50 // the obvious thing.
  51 //
  52 // Why integral expressions, and not functions nor types?
  53 // Firstly, these compile-time entities are used as template-arguments
  54 // so function return values won't work:  We need compile-time entities.
  55 // We're left with types and constant  integral expressions.
  56 // Secondly, from the point of view of ease of use, type-based compile-time
  57 // information is -not- *that* convenient.  On has to write lots of
  58 // overloaded functions and to hope that the compiler will select the right
  59 // one. As a net effect, the overall structure isn't very clear at first
  60 // glance.
  61 // Thirdly, partial ordering and overload resolution (of function templates)
  62 // is highly costly in terms of compiler-resource.  It is a Good Thing to
  63 // keep these resource consumption as least as possible.
  64 //
  65 // See valarray_array.h for a case use.
  66 //
  67 // -- Gaby (dosreis@cmla.ens-cachan.fr) 2000-03-06.
  68 //
  69 // Update 2005: types are also provided and <bits/type_traits.h> has been
  70 // removed.
  71 //
  72
  73 // Forward declaration hack, should really include this from somewhere.
  74 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
  75
  76   template<typename _Iterator, typename _Container>
  77     class __normal_iterator;
  78
  79 _GLIBCXX_END_NAMESPACE
  80
  81 _GLIBCXX_BEGIN_NAMESPACE(std)
  82
  83   struct __true_type { };
  84   struct __false_type { };
  85
  86   template<bool>
  87     struct __truth_type
  88     { typedef __false_type __type; };
  89
  90   template<>
  91     struct __truth_type<true>
  92     { typedef __true_type __type; };
  93
  94   // N.B. The conversions to bool are needed due to the issue
  95   // explained in c++/19404.
  96   template<class _Sp, class _Tp>
  97     struct __traitor
  98     {
  99       enum { __value = bool(_Sp::__value) || bool(_Tp::__value) };
 100       typedef typename __truth_type<__value>::__type __type;
 101     };
 102
 103   // Compare for equality of types.
 104   template<typename, typename>
 105     struct __are_same
 106     {
 107       enum { __value = 0 };
 108       typedef __false_type __type;
 109     };
 110
 111   template<typename _Tp>
 112     struct __are_same<_Tp, _Tp>
 113     {
 114       enum { __value = 1 };
 115       typedef __true_type __type;
 116     };
 117
 118   // Holds if the template-argument is a void type.
 119   template<typename _Tp>
 120     struct __is_void
 121     {
 122       enum { __value = 0 };
 123       typedef __false_type __type;
 124     };
 125
 126   template<>
 127     struct __is_void<void>
 128     {
 129       enum { __value = 1 };
 130       typedef __true_type __type;
 131     };
 132
 133   //
 134   // Integer types
 135   //
 136   template<typename _Tp>
 137     struct __is_integer
 138     {
 139       enum { __value = 0 };
 140       typedef __false_type __type;
 141     };
 142
 143   // Thirteen specializations (yes there are eleven standard integer
 144   // types; 'long long' and 'unsigned long long' are supported as
 145   // extensions)
 146   template<>
 147     struct __is_integer<bool>
 148     {
 149       enum { __value = 1 };
 150       typedef __true_type __type;
 151     };
 152
 153   template<>
 154     struct __is_integer<char>
 155     {
 156       enum { __value = 1 };
 157       typedef __true_type __type;
 158     };
 159
 160   template<>
 161     struct __is_integer<signed char>
 162     {
 163       enum { __value = 1 };
 164       typedef __true_type __type;
 165     };
 166
 167   template<>
 168     struct __is_integer<unsigned char>
 169     {
 170       enum { __value = 1 };
 171       typedef __true_type __type;
 172     };
 173
 174 # ifdef _GLIBCXX_USE_WCHAR_T
 175   template<>
 176     struct __is_integer<wchar_t>
 177     {
 178       enum { __value = 1 };
 179       typedef __true_type __type;
 180     };
 181 # endif
 182
 183 #ifdef __GXX_EXPERIMENTAL_CXX0X__
 184   template<>
 185     struct __is_integer<char16_t>
 186     {
 187       enum { __value = 1 };
 188       typedef __true_type __type;
 189     };
 190
 191   template<>
 192     struct __is_integer<char32_t>
 193     {
 194       enum { __value = 1 };
 195       typedef __true_type __type;
 196     };
 197 #endif
 198
 199   template<>
 200     struct __is_integer<short>
 201     {
 202       enum { __value = 1 };
 203       typedef __true_type __type;
 204     };
 205
 206   template<>
 207     struct __is_integer<unsigned short>
 208     {
 209       enum { __value = 1 };
 210       typedef __true_type __type;
 211     };
 212
 213   template<>
 214     struct __is_integer<int>
 215     {
 216       enum { __value = 1 };
 217       typedef __true_type __type;
 218     };
 219
 220   template<>
 221     struct __is_integer<unsigned int>
 222     {
 223       enum { __value = 1 };
 224       typedef __true_type __type;
 225     };
 226
 227   template<>
 228     struct __is_integer<long>
 229     {
 230       enum { __value = 1 };
 231       typedef __true_type __type;
 232     };
 233
 234   template<>
 235     struct __is_integer<unsigned long>
 236     {
 237       enum { __value = 1 };
 238       typedef __true_type __type;
 239     };
 240
 241   template<>
 242     struct __is_integer<long long>
 243     {
 244       enum { __value = 1 };
 245       typedef __true_type __type;
 246     };
 247
 248   template<>
 249     struct __is_integer<unsigned long long>
 250     {
 251       enum { __value = 1 };
 252       typedef __true_type __type;
 253     };
 254
 255   //
 256   // Floating point types
 257   //
 258   template<typename _Tp>
 259     struct __is_floating
 260     {
 261       enum { __value = 0 };
 262       typedef __false_type __type;
 263     };
 264
 265   // three specializations (float, double and 'long double')
 266   template<>
 267     struct __is_floating<float>
 268     {
 269       enum { __value = 1 };
 270       typedef __true_type __type;
 271     };
 272
 273   template<>
 274     struct __is_floating<double>
 275     {
 276       enum { __value = 1 };
 277       typedef __true_type __type;
 278     };
 279
 280   template<>
 281     struct __is_floating<long double>
 282     {
 283       enum { __value = 1 };
 284       typedef __true_type __type;
 285     };
 286
 287   //
 288   // Pointer types
 289   //
 290   template<typename _Tp>
 291     struct __is_pointer
 292     {
 293       enum { __value = 0 };
 294       typedef __false_type __type;
 295     };
 296
 297   template<typename _Tp>
 298     struct __is_pointer<_Tp*>
 299     {
 300       enum { __value = 1 };
 301       typedef __true_type __type;
 302     };
 303
 304   //
 305   // Normal iterator type
 306   //
 307   template<typename _Tp>
 308     struct __is_normal_iterator
 309     {
 310       enum { __value = 0 };
 311       typedef __false_type __type;
 312     };
 313
 314   template<typename _Iterator, typename _Container>
 315     struct __is_normal_iterator< __gnu_cxx::__normal_iterator<_Iterator,
 316                                                               _Container> >
 317     {
 318       enum { __value = 1 };
 319       typedef __true_type __type;
 320     };
 321
 322   //
 323   // An arithmetic type is an integer type or a floating point type
 324   //
 325   template<typename _Tp>
 326     struct __is_arithmetic
 327     : public __traitor<__is_integer<_Tp>, __is_floating<_Tp> >
 328     { };
 329
 330   //
 331   // A fundamental type is `void' or and arithmetic type
 332   //
 333   template<typename _Tp>
 334     struct __is_fundamental
 335     : public __traitor<__is_void<_Tp>, __is_arithmetic<_Tp> >
 336     { };
 337
 338   //
 339   // A scalar type is an arithmetic type or a pointer type
 340   //
 341   template<typename _Tp>
 342     struct __is_scalar
 343     : public __traitor<__is_arithmetic<_Tp>, __is_pointer<_Tp> >
 344     { };
 345
 346   //
 347   // For use in std::copy and std::find overloads for streambuf iterators.
 348   //
 349   template<typename _Tp>
 350     struct __is_char
 351     {
 352       enum { __value = 0 };
 353       typedef __false_type __type;
 354     };
 355
 356   template<>
 357     struct __is_char<char>
 358     {
 359       enum { __value = 1 };
 360       typedef __true_type __type;
 361     };
 362
 363 #ifdef _GLIBCXX_USE_WCHAR_T
 364   template<>
 365     struct __is_char<wchar_t>
 366     {
 367       enum { __value = 1 };
 368       typedef __true_type __type;
 369     };
 370 #endif
 371
 372   template<typename _Tp>
 373     struct __is_byte
 374     {
 375       enum { __value = 0 };
 376       typedef __false_type __type;
 377     };
 378
 379   template<>
 380     struct __is_byte<char>
 381     {
 382       enum { __value = 1 };
 383       typedef __true_type __type;
 384     };
 385
 386   template<>
 387     struct __is_byte<signed char>
 388     {
 389       enum { __value = 1 };
 390       typedef __true_type __type;
 391     };
 392
 393   template<>
 394     struct __is_byte<unsigned char>
 395     {
 396       enum { __value = 1 };
 397       typedef __true_type __type;
 398     };
 399
 400   //
 401   // Move iterator type
 402   //
 403   template<typename _Tp>
 404     struct __is_move_iterator
 405     {
 406       enum { __value = 0 };
 407       typedef __false_type __type;
 408     };
 409
 410 #ifdef __GXX_EXPERIMENTAL_CXX0X__
 411   template<typename _Iterator>
 412     class move_iterator;
 413
 414   template<typename _Iterator>
 415     struct __is_move_iterator< move_iterator<_Iterator> >
 416     {
 417       enum { __value = 1 };
 418       typedef __true_type __type;
 419     };
 420 #endif
 421
 422 _GLIBCXX_END_NAMESPACE
 423
 424 #endif //_CPP_TYPE_TRAITS_H