numeric_traits.h

Go to the documentation of this file.

// -*- C++ -*-

// Copyright (C) 2007-2018 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the terms
// of the GNU General Public License as published by the Free Software
// Foundation; either version 3, or (at your option) any later
// version.

// This library is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file ext/numeric_traits.h
 *  This file is a GNU extension to the Standard C++ Library.
 */

#ifndef _EXT_NUMERIC_TRAITS
#define _EXT_NUMERIC_TRAITS 1

#pragma GCC system_header

#include <bits/cpp_type_traits.h>
#include <ext/type_traits.h>

namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  // Compile time constants for builtin types.
  // Sadly std::numeric_limits member functions cannot be used for this.
#define __glibcxx_signed(_Tp) ((_Tp)(-1) < 0)
#define __glibcxx_digits(_Tp) \
  (sizeof(_Tp) * __CHAR_BIT__ - __glibcxx_signed(_Tp))

#define __glibcxx_min(_Tp) \
  (__glibcxx_signed(_Tp) ? (_Tp)1 << __glibcxx_digits(_Tp) : (_Tp)0)

#define __glibcxx_max(_Tp) \
  (__glibcxx_signed(_Tp) ? \
   (((((_Tp)1 << (__glibcxx_digits(_Tp) - 1)) - 1) << 1) + 1) : ~(_Tp)0)

  template<typename _Value>
    struct __numeric_traits_integer
    {
      // Only integers for initialization of member constant.
      static const _Value __min = __glibcxx_min(_Value);
      static const _Value __max = __glibcxx_max(_Value);

      // NB: these two also available in std::numeric_limits as compile
      // time constants, but <limits> is big and we avoid including it.
      static const bool __is_signed = __glibcxx_signed(_Value);
      static const int __digits = __glibcxx_digits(_Value);      
    };

  template<typename _Value>
    const _Value __numeric_traits_integer<_Value>::__min;

  template<typename _Value>
    const _Value __numeric_traits_integer<_Value>::__max;

  template<typename _Value>
    const bool __numeric_traits_integer<_Value>::__is_signed;

  template<typename _Value>
    const int __numeric_traits_integer<_Value>::__digits;

#undef __glibcxx_signed
#undef __glibcxx_digits
#undef __glibcxx_min
#undef __glibcxx_max

#define __glibcxx_floating(_Tp, _Fval, _Dval, _LDval) \
  (std::__are_same<_Tp, float>::__value ? _Fval \
   : std::__are_same<_Tp, double>::__value ? _Dval : _LDval)

#define __glibcxx_max_digits10(_Tp) \
  (2 + __glibcxx_floating(_Tp, __FLT_MANT_DIG__, __DBL_MANT_DIG__, \
                          __LDBL_MANT_DIG__) * 643L / 2136)

#define __glibcxx_digits10(_Tp) \
  __glibcxx_floating(_Tp, __FLT_DIG__, __DBL_DIG__, __LDBL_DIG__)

#define __glibcxx_max_exponent10(_Tp) \
  __glibcxx_floating(_Tp, __FLT_MAX_10_EXP__, __DBL_MAX_10_EXP__, \
                     __LDBL_MAX_10_EXP__)

  template<typename _Value>
    struct __numeric_traits_floating
    {
      // Only floating point types. See N1822. 
      static const int __max_digits10 = __glibcxx_max_digits10(_Value);

      // See above comment...
      static const bool __is_signed = true;
      static const int __digits10 = __glibcxx_digits10(_Value);
      static const int __max_exponent10 = __glibcxx_max_exponent10(_Value);
    };

  template<typename _Value>
    const int __numeric_traits_floating<_Value>::__max_digits10;

  template<typename _Value>
    const bool __numeric_traits_floating<_Value>::__is_signed;

  template<typename _Value>
    const int __numeric_traits_floating<_Value>::__digits10;

  template<typename _Value>
    const int __numeric_traits_floating<_Value>::__max_exponent10;

  template<typename _Value>
    struct __numeric_traits
    : public __conditional_type<std::__is_integer<_Value>::__value,
                                __numeric_traits_integer<_Value>,
                                __numeric_traits_floating<_Value> >::__type
    { };

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

#undef __glibcxx_floating
#undef __glibcxx_max_digits10
#undef __glibcxx_digits10
#undef __glibcxx_max_exponent10

#endif