libstdc++-v3/include/ext/type_traits.h

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the terms
   7 // of the GNU General Public License as published by the Free Software
   8 // Foundation; either version 2, or (at your option) any later
   9 // version.
  10
  11 // This library is distributed in the hope that it will be useful, but
  12 // WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 // General Public License for more details.
  15
  16 // You should have received a copy of the GNU General Public License along
  17 // with this library; see the file COPYING.  If not, write to the Free
  18 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  19 // USA.
  20
  21 // As a special exception, you may use this file as part of a free
  22 // software library without restriction.  Specifically, if other files
  23 // instantiate templates or use macros or inline functions from this
  24 // file, or you compile this file and link it with other files to
  25 // produce an executable, this file does not by itself cause the
  26 // resulting executable to be covered by the GNU General Public
  27 // License.  This exception does not however invalidate any other
  28 // reasons why the executable file might be covered by the GNU General
  29 // Public License.
  30
  31 /** @file ext/type_traits.h
  32  *  This file is a GNU extension to the Standard C++ Library.
  33  */
  34
  35 #ifndef _EXT_TYPE_TRAITS
  36 #define _EXT_TYPE_TRAITS 1
  37
  38 #pragma GCC system_header
  39
  40 #include <limits>
  41 #include <bits/cpp_type_traits.h>
  42
  43 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
  44
  45   // Define a nested type if some predicate holds.
  46   template<bool, typename>
  47     struct __enable_if
  48     { };
  49
  50   template<typename _Tp>
  51     struct __enable_if<true, _Tp>
  52     { typedef _Tp __type; };
  53
  54
  55   // Conditional expression for types. If true, first, if false, second.
  56   template<bool _Cond, typename _Iftrue, typename _Iffalse>
  57     struct __conditional_type
  58     { typedef _Iftrue __type; };
  59
  60   template<typename _Iftrue, typename _Iffalse>
  61     struct __conditional_type<false, _Iftrue, _Iffalse>
  62     { typedef _Iffalse __type; };
  63
  64
  65   // Given an integral builtin type, return the corresponding unsigned type.
  66   template<typename _Tp>
  67     struct __add_unsigned
  68     {
  69     private:
  70       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
  71
  72     public:
  73       typedef typename __if_type::__type __type;
  74     };
  75
  76   template<>
  77     struct __add_unsigned<char>
  78     { typedef unsigned char __type; };
  79
  80   template<>
  81     struct __add_unsigned<signed char>
  82     { typedef unsigned char __type; };
  83
  84   template<>
  85     struct __add_unsigned<short>
  86     { typedef unsigned short __type; };
  87
  88   template<>
  89     struct __add_unsigned<int>
  90     { typedef unsigned int __type; };
  91
  92   template<>
  93     struct __add_unsigned<long>
  94     { typedef unsigned long __type; };
  95
  96   template<>
  97     struct __add_unsigned<long long>
  98     { typedef unsigned long long __type; };
  99
 100   // Declare but don't define.
 101   template<>
 102     struct __add_unsigned<bool>;
 103
 104   template<>
 105     struct __add_unsigned<wchar_t>;
 106
 107
 108   // Given an integral builtin type, return the corresponding signed type.
 109   template<typename _Tp>
 110     struct __remove_unsigned
 111     {
 112     private:
 113       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
 114
 115     public:
 116       typedef typename __if_type::__type __type;
 117     };
 118
 119   template<>
 120     struct __remove_unsigned<char>
 121     { typedef signed char __type; };
 122
 123   template<>
 124     struct __remove_unsigned<unsigned char>
 125     { typedef signed char __type; };
 126
 127   template<>
 128     struct __remove_unsigned<unsigned short>
 129     { typedef short __type; };
 130
 131   template<>
 132     struct __remove_unsigned<unsigned int>
 133     { typedef int __type; };
 134
 135   template<>
 136     struct __remove_unsigned<unsigned long>
 137     { typedef long __type; };
 138
 139   template<>
 140     struct __remove_unsigned<unsigned long long>
 141     { typedef long long __type; };
 142
 143   // Declare but don't define.
 144   template<>
 145     struct __remove_unsigned<bool>;
 146
 147   template<>
 148     struct __remove_unsigned<wchar_t>;
 149
 150
 151   // Compile time constants for builtin types.
 152   // Sadly std::numeric_limits member functions cannot be used for this.
 153 #define __glibcxx_signed(_Tp) ((_Tp)(-1) < 0)
 154 #define __glibcxx_digits(_Tp) \
 155   (sizeof(_Tp) * __CHAR_BIT__ - __glibcxx_signed(_Tp))
 156
 157 #define __glibcxx_min(_Tp) \
 158   (__glibcxx_signed(_Tp) ? (_Tp)1 << __glibcxx_digits(_Tp) : (_Tp)0)
 159
 160 #define __glibcxx_max(_Tp) \
 161   (__glibcxx_signed(_Tp) ? \
 162    (((((_Tp)1 << (__glibcxx_digits(_Tp) - 1)) - 1) << 1) + 1) : ~(_Tp)0)
 163
 164   template<typename _Value>
 165     struct __numeric_traits_integer
 166     {
 167       // Only integers for initialization of member constant.
 168       static const _Value __min = __glibcxx_min(_Value);
 169       static const _Value __max = __glibcxx_max(_Value);
 170     };
 171
 172   template<typename _Value>
 173     const _Value __numeric_traits_integer<_Value>::__min;
 174
 175   template<typename _Value>
 176     const _Value __numeric_traits_integer<_Value>::__max;
 177
 178   template<typename _Value>
 179     struct __numeric_traits_floating
 180     {
 181       // Only floating point types. See N1822.
 182       static const int __max_digits10 =
 183         2 + std::numeric_limits<_Value>::digits * 3010/10000;
 184     };
 185
 186   template<typename _Value>
 187     const int __numeric_traits_floating<_Value>::__max_digits10;
 188
 189   template<typename _Value>
 190     struct __numeric_traits
 191     : public __conditional_type<std::__is_integer<_Value>::__value,
 192                                 __numeric_traits_integer<_Value>,
 193                                 __numeric_traits_floating<_Value> >::__type
 194     { };
 195
 196 _GLIBCXX_END_NAMESPACE
 197
 198 #undef __glibcxx_signed
 199 #undef __glibcxx_min
 200 #undef __glibcxx_max
 201 #undef __glibcxx_digits
 202
 203 #endif