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

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 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/numeric_traits.h
  32  *  This file is a GNU extension to the Standard C++ Library.
  33  */
  34
  35 #ifndef _EXT_NUMERIC_TRAITS
  36 #define _EXT_NUMERIC_TRAITS 1
  37
  38 #pragma GCC system_header
  39
  40 #include <limits>
  41 #include <bits/cpp_type_traits.h>
  42 #include <ext/type_traits.h>
  43
  44 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
  45
  46   // Compile time constants for builtin types.
  47   // Sadly std::numeric_limits member functions cannot be used for this.
  48 #define __glibcxx_signed(_Tp) ((_Tp)(-1) < 0)
  49 #define __glibcxx_digits(_Tp) \
  50   (sizeof(_Tp) * __CHAR_BIT__ - __glibcxx_signed(_Tp))
  51
  52 #define __glibcxx_min(_Tp) \
  53   (__glibcxx_signed(_Tp) ? (_Tp)1 << __glibcxx_digits(_Tp) : (_Tp)0)
  54
  55 #define __glibcxx_max(_Tp) \
  56   (__glibcxx_signed(_Tp) ? \
  57    (((((_Tp)1 << (__glibcxx_digits(_Tp) - 1)) - 1) << 1) + 1) : ~(_Tp)0)
  58
  59   template<typename _Value>
  60     struct __numeric_traits_integer
  61     {
  62       // Only integers for initialization of member constant.
  63       static const _Value __min = __glibcxx_min(_Value);
  64       static const _Value __max = __glibcxx_max(_Value);
  65     };
  66
  67   template<typename _Value>
  68     const _Value __numeric_traits_integer<_Value>::__min;
  69
  70   template<typename _Value>
  71     const _Value __numeric_traits_integer<_Value>::__max;
  72
  73   template<typename _Value>
  74     struct __numeric_traits_floating
  75     {
  76       // Only floating point types. See N1822.
  77       static const int __max_digits10 =
  78         2 + std::numeric_limits<_Value>::digits * 3010/10000;
  79     };
  80
  81   template<typename _Value>
  82     const int __numeric_traits_floating<_Value>::__max_digits10;
  83
  84   template<typename _Value>
  85     struct __numeric_traits
  86     : public __conditional_type<std::__is_integer<_Value>::__value,
  87                                 __numeric_traits_integer<_Value>,
  88                                 __numeric_traits_floating<_Value> >::__type
  89     { };
  90
  91 _GLIBCXX_END_NAMESPACE
  92
  93 #undef __glibcxx_signed
  94 #undef __glibcxx_min
  95 #undef __glibcxx_max
  96 #undef __glibcxx_digits
  97
  98 #endif