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

// -*- C++ -*-

// Copyright (C) 2005, 2006, 2007 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 2, 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.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.

// As a special exception, you may use this file as part of a free
// software library without restriction.  Specifically, if other files
// instantiate templates or use macros or inline functions from this
// file, or you compile this file and link it with other files to
// produce an executable, this file does not by itself cause the
// resulting executable to be covered by the GNU General Public
// License.  This exception does not however invalidate any other
// reasons why the executable file might be covered by the GNU General
// Public License.

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

#ifndef _EXT_TYPE_TRAITS
#define _EXT_TYPE_TRAITS 1

#pragma GCC system_header

#include <limits>
#include <bits/cpp_type_traits.h>

_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)

  // Define a nested type if some predicate holds.
  template<bool, typename>
    struct __enable_if 
    { };

  template<typename _Tp>
    struct __enable_if<true, _Tp>
    { typedef _Tp __type; };


  // Conditional expression for types. If true, first, if false, second.
  template<bool _Cond, typename _Iftrue, typename _Iffalse>
    struct __conditional_type
    { typedef _Iftrue __type; };

  template<typename _Iftrue, typename _Iffalse>
    struct __conditional_type<false, _Iftrue, _Iffalse>
    { typedef _Iffalse __type; };


  // Given an integral builtin type, return the corresponding unsigned type.
  template<typename _Tp>
    struct __add_unsigned
    { 
    private:
      typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
      
    public:
      typedef typename __if_type::__type __type; 
    };

  template<>
    struct __add_unsigned<char>
    { typedef unsigned char __type; };

  template<>
    struct __add_unsigned<signed char>
    { typedef unsigned char __type; };

  template<>
    struct __add_unsigned<short>
    { typedef unsigned short __type; };

  template<>
    struct __add_unsigned<int>
    { typedef unsigned int __type; };

  template<>
    struct __add_unsigned<long>
    { typedef unsigned long __type; };

  template<>
    struct __add_unsigned<long long>
    { typedef unsigned long long __type; };

  // Declare but don't define.
  template<>
    struct __add_unsigned<bool>;

  template<>
    struct __add_unsigned<wchar_t>;


  // Given an integral builtin type, return the corresponding signed type.
  template<typename _Tp>
    struct __remove_unsigned
    { 
    private:
      typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
      
    public:
      typedef typename __if_type::__type __type; 
    };

  template<>
    struct __remove_unsigned<char>
    { typedef signed char __type; };

  template<>
    struct __remove_unsigned<unsigned char>
    { typedef signed char __type; };

  template<>
    struct __remove_unsigned<unsigned short>
    { typedef short __type; };

  template<>
    struct __remove_unsigned<unsigned int>
    { typedef int __type; };

  template<>
    struct __remove_unsigned<unsigned long>
    { typedef long __type; };

  template<>
    struct __remove_unsigned<unsigned long long>
    { typedef long long __type; };

  // Declare but don't define.
  template<>
    struct __remove_unsigned<bool>;

  template<>
    struct __remove_unsigned<wchar_t>;


  // 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);
    };

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

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

  template<typename _Value>
    struct __numeric_traits_floating
    {
      // Only floating point types. See N1822. 
      static const int __max_digits10 =
	2 + std::numeric_limits<_Value>::digits * 3010/10000;
    };

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

  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

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

#endif