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

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2007, 2008, 2009, 2010 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 3, 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 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /** @file ext/numeric_traits.h
  26  *  This file is a GNU extension to the Standard C++ Library.
  27  */
  28
  29 #ifndef _EXT_NUMERIC_TRAITS
  30 #define _EXT_NUMERIC_TRAITS 1
  31
  32 #pragma GCC system_header
  33
  34 #include <bits/cpp_type_traits.h>
  35 #include <ext/type_traits.h>
  36
  37 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
  38
  39   // Compile time constants for builtin types.
  40   // Sadly std::numeric_limits member functions cannot be used for this.
  41 #define __glibcxx_signed(_Tp) ((_Tp)(-1) < 0)
  42 #define __glibcxx_digits(_Tp) \
  43   (sizeof(_Tp) * __CHAR_BIT__ - __glibcxx_signed(_Tp))
  44
  45 #define __glibcxx_min(_Tp) \
  46   (__glibcxx_signed(_Tp) ? (_Tp)1 << __glibcxx_digits(_Tp) : (_Tp)0)
  47
  48 #define __glibcxx_max(_Tp) \
  49   (__glibcxx_signed(_Tp) ? \
  50    (((((_Tp)1 << (__glibcxx_digits(_Tp) - 1)) - 1) << 1) + 1) : ~(_Tp)0)
  51
  52   template<typename _Value>
  53     struct __numeric_traits_integer
  54     {
  55       // Only integers for initialization of member constant.
  56       static const _Value __min = __glibcxx_min(_Value);
  57       static const _Value __max = __glibcxx_max(_Value);
  58
  59       // NB: these two also available in std::numeric_limits as compile
  60       // time constants, but <limits> is big and we avoid including it.
  61       static const bool __is_signed = __glibcxx_signed(_Value);
  62       static const int __digits = __glibcxx_digits(_Value);
  63     };
  64
  65   template<typename _Value>
  66     const _Value __numeric_traits_integer<_Value>::__min;
  67
  68   template<typename _Value>
  69     const _Value __numeric_traits_integer<_Value>::__max;
  70
  71   template<typename _Value>
  72     const bool __numeric_traits_integer<_Value>::__is_signed;
  73
  74   template<typename _Value>
  75     const int __numeric_traits_integer<_Value>::__digits;
  76
  77 #undef __glibcxx_signed
  78 #undef __glibcxx_digits
  79 #undef __glibcxx_min
  80 #undef __glibcxx_max
  81
  82 #define __glibcxx_floating(_Tp, _Fval, _Dval, _LDval) \
  83   (std::__are_same<_Tp, float>::__value ? _Fval \
  84    : std::__are_same<_Tp, double>::__value ? _Dval : _LDval)
  85
  86 #define __glibcxx_max_digits10(_Tp) \
  87   (2 + __glibcxx_floating(_Tp, __FLT_MANT_DIG__, __DBL_MANT_DIG__, \
  88                           __LDBL_MANT_DIG__) * 643L / 2136)
  89
  90 #define __glibcxx_digits10(_Tp) \
  91   __glibcxx_floating(_Tp, __FLT_DIG__, __DBL_DIG__, __LDBL_DIG__)
  92
  93 #define __glibcxx_max_exponent10(_Tp) \
  94   __glibcxx_floating(_Tp, __FLT_MAX_10_EXP__, __DBL_MAX_10_EXP__, \
  95                      __LDBL_MAX_10_EXP__)
  96
  97   template<typename _Value>
  98     struct __numeric_traits_floating
  99     {
 100       // Only floating point types. See N1822.
 101       static const int __max_digits10 = __glibcxx_max_digits10(_Value);
 102
 103       // See above comment...
 104       static const bool __is_signed = true;
 105       static const int __digits10 = __glibcxx_digits10(_Value);
 106       static const int __max_exponent10 = __glibcxx_max_exponent10(_Value);
 107     };
 108
 109   template<typename _Value>
 110     const int __numeric_traits_floating<_Value>::__max_digits10;
 111
 112   template<typename _Value>
 113     const bool __numeric_traits_floating<_Value>::__is_signed;
 114
 115   template<typename _Value>
 116     const int __numeric_traits_floating<_Value>::__digits10;
 117
 118   template<typename _Value>
 119     const int __numeric_traits_floating<_Value>::__max_exponent10;
 120
 121   template<typename _Value>
 122     struct __numeric_traits
 123     : public __conditional_type<std::__is_integer<_Value>::__value,
 124                                 __numeric_traits_integer<_Value>,
 125                                 __numeric_traits_floating<_Value> >::__type
 126     { };
 127
 128 _GLIBCXX_END_NAMESPACE
 129
 130 #undef __glibcxx_floating
 131 #undef __glibcxx_max_digits10
 132 #undef __glibcxx_digits10
 133 #undef __glibcxx_max_exponent10
 134
 135 #endif