ext/numeric_traits.h
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// -*- C++ -*-
// Copyright (C) 2007-2021 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.
// In C++98 std::numeric_limits member functions are not constant expressions
// (that changed in C++11 with the addition of 'constexpr').
// Even for C++11, this header is smaller than <limits> and can be used
// when only is_signed, digits, min, or max values are needed for integers,
// or is_signed, digits10, max_digits10, or max_exponent10 for floats.
// Unlike __is_integer (and std::is_integral) this trait is true for
// non-standard built-in integer types such as __int128 and __int20.
template<typename _Tp>
struct __is_integer_nonstrict
: public std::__is_integer<_Tp>
{
using std::__is_integer<_Tp>::__value;
// The number of bits in the value representation.
enum { __width = __value ? sizeof(_Tp) * __CHAR_BIT__ : 0 };
};
template<typename _Value>
struct __numeric_traits_integer
{
#if __cplusplus >= 201103L
static_assert(__is_integer_nonstrict<_Value>::__value,
"invalid specialization");
#endif
// NB: these two are also available in std::numeric_limits as compile
// time constants, but <limits> is big and we can avoid including it.
static const bool __is_signed = (_Value)(-1) < 0;
static const int __digits
= __is_integer_nonstrict<_Value>::__width - __is_signed;
// The initializers must be constants so that __max and __min are too.
static const _Value __max = __is_signed
? (((((_Value)1 << (__digits - 1)) - 1) << 1) + 1)
: ~(_Value)0;
static const _Value __min = __is_signed ? -__max - 1 : (_Value)0;
};
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;
// Enable __numeric_traits_integer for types where the __is_integer_nonstrict
// primary template doesn't give the right answer.
#define _GLIBCXX_INT_N_TRAITS(T, WIDTH) \
template<> struct __is_integer_nonstrict<T> \
{ \
enum { __value = 1 }; \
typedef std::__true_type __type; \
enum { __width = WIDTH }; \
}; \
template<> struct __is_integer_nonstrict<unsigned T> \
{ \
enum { __value = 1 }; \
typedef std::__true_type __type; \
enum { __width = WIDTH }; \
};
// We need to specify the width for some __intNN types because they
// have padding bits, e.g. the object representation of __int20 has 32 bits,
// but its width (number of bits in the value representation) is only 20.
#if defined __GLIBCXX_TYPE_INT_N_0 && __GLIBCXX_BITSIZE_INT_N_0 % __CHAR_BIT__
_GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_0, __GLIBCXX_BITSIZE_INT_N_0)
#endif
#if defined __GLIBCXX_TYPE_INT_N_1 && __GLIBCXX_BITSIZE_INT_N_1 % __CHAR_BIT__
_GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_1, __GLIBCXX_BITSIZE_INT_N_1)
#endif
#if defined __GLIBCXX_TYPE_INT_N_2 && __GLIBCXX_BITSIZE_INT_N_2 % __CHAR_BIT__
_GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_2, __GLIBCXX_BITSIZE_INT_N_2)
#endif
#if defined __GLIBCXX_TYPE_INT_N_3 && __GLIBCXX_BITSIZE_INT_N_3 % __CHAR_BIT__
_GLIBCXX_INT_N_TRAITS(__GLIBCXX_TYPE_INT_N_3, __GLIBCXX_BITSIZE_INT_N_3)
#endif
#if defined __STRICT_ANSI__ && defined __SIZEOF_INT128__
// In strict modes __is_integer<__int128> is false,
// but we still want to define __numeric_traits_integer<__int128>.
_GLIBCXX_INT_N_TRAITS(__int128, 128)
#endif
#undef _GLIBCXX_INT_N_TRAITS
#if __cplusplus >= 201103L
/// Convenience alias for __numeric_traits<integer-type>.
template<typename _Tp>
using __int_traits = __numeric_traits_integer<_Tp>;
#endif
#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__)
// N.B. this only supports float, double and long double (no __float128 etc.)
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;
#undef __glibcxx_floating
#undef __glibcxx_max_digits10
#undef __glibcxx_digits10
#undef __glibcxx_max_exponent10
template<typename _Value>
struct __numeric_traits
: public __numeric_traits_integer<_Value>
{ };
template<>
struct __numeric_traits<float>
: public __numeric_traits_floating<float>
{ };
template<>
struct __numeric_traits<double>
: public __numeric_traits_floating<double>
{ };
template<>
struct __numeric_traits<long double>
: public __numeric_traits_floating<long double>
{ };
#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
# if defined __LONG_DOUBLE_IEEE128__
// long double is __ieee128, define traits for __ibm128
template<>
struct __numeric_traits_floating<__ibm128>
{
static const int __max_digits10 = 33;
static const bool __is_signed = true;
static const int __digits10 = 31;
static const int __max_exponent10 = 308;
};
template<>
struct __numeric_traits<__ibm128>
: public __numeric_traits_floating<__ibm128>
{ };
# elif defined __LONG_DOUBLE_IBM128__
// long double is __ibm128, define traits for __ieee128
template<>
struct __numeric_traits_floating<__ieee128>
{
static const int __max_digits10 = 36;
static const bool __is_signed = true;
static const int __digits10 = 33;
static const int __max_exponent10 = 4932;
};
template<>
struct __numeric_traits<__ieee128>
: public __numeric_traits_floating<__ieee128>
{ };
# endif
#endif
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif
cpp_type_traits.h
type_traits.h
__gnu_cxx
GNU extensions for public use.
__gnu_cxx::__int_traits
__numeric_traits_integer< _Tp > __int_traits
Convenience alias for __numeric_traits<integer-type>.
Definition ext/numeric_traits.h:136