cpp_type_traits.h
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// The -*- C++ -*- type traits classes for internal use in libstdc++
// Copyright (C) 2000-2018 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 bits/cpp_type_traits.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{ext/type_traits}
*/
// Written by Gabriel Dos Reis <dosreis@cmla.ens-cachan.fr>
#ifndef _CPP_TYPE_TRAITS_H
#define _CPP_TYPE_TRAITS_H 1
#pragma GCC system_header
#include <bits/c++config.h>
//
// This file provides some compile-time information about various types.
// These representations were designed, on purpose, to be constant-expressions
// and not types as found in <bits/type_traits.h>. In particular, they
// can be used in control structures and the optimizer hopefully will do
// the obvious thing.
//
// Why integral expressions, and not functions nor types?
// Firstly, these compile-time entities are used as template-arguments
// so function return values won't work: We need compile-time entities.
// We're left with types and constant integral expressions.
// Secondly, from the point of view of ease of use, type-based compile-time
// information is -not- *that* convenient. On has to write lots of
// overloaded functions and to hope that the compiler will select the right
// one. As a net effect, the overall structure isn't very clear at first
// glance.
// Thirdly, partial ordering and overload resolution (of function templates)
// is highly costly in terms of compiler-resource. It is a Good Thing to
// keep these resource consumption as least as possible.
//
// See valarray_array.h for a case use.
//
// -- Gaby (dosreis@cmla.ens-cachan.fr) 2000-03-06.
//
// Update 2005: types are also provided and <bits/type_traits.h> has been
// removed.
//
extern "C++" {
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
struct __true_type { };
struct __false_type { };
template<bool>
struct __truth_type
{ typedef __false_type __type; };
template<>
struct __truth_type<true>
{ typedef __true_type __type; };
// N.B. The conversions to bool are needed due to the issue
// explained in c++/19404.
template<class _Sp, class _Tp>
struct __traitor
{
enum { __value = bool(_Sp::__value) || bool(_Tp::__value) };
typedef typename __truth_type<__value>::__type __type;
};
// Compare for equality of types.
template<typename, typename>
struct __are_same
{
enum { __value = 0 };
typedef __false_type __type;
};
template<typename _Tp>
struct __are_same<_Tp, _Tp>
{
enum { __value = 1 };
typedef __true_type __type;
};
// Holds if the template-argument is a void type.
template<typename _Tp>
struct __is_void
{
enum { __value = 0 };
typedef __false_type __type;
};
template<>
struct __is_void<void>
{
enum { __value = 1 };
typedef __true_type __type;
};
//
// Integer types
//
template<typename _Tp>
struct __is_integer
{
enum { __value = 0 };
typedef __false_type __type;
};
// Thirteen specializations (yes there are eleven standard integer
// types; <em>long long</em> and <em>unsigned long long</em> are
// supported as extensions). Up to four target-specific __int<N>
// types are supported as well.
template<>
struct __is_integer<bool>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_integer<char>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_integer<signed char>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_integer<unsigned char>
{
enum { __value = 1 };
typedef __true_type __type;
};
# ifdef _GLIBCXX_USE_WCHAR_T
template<>
struct __is_integer<wchar_t>
{
enum { __value = 1 };
typedef __true_type __type;
};
# endif
#if __cplusplus >= 201103L
template<>
struct __is_integer<char16_t>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_integer<char32_t>
{
enum { __value = 1 };
typedef __true_type __type;
};
#endif
template<>
struct __is_integer<short>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_integer<unsigned short>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_integer<int>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_integer<unsigned int>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_integer<long>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_integer<unsigned long>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_integer<long long>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_integer<unsigned long long>
{
enum { __value = 1 };
typedef __true_type __type;
};
#define __INT_N(TYPE) \
template<> \
struct __is_integer<TYPE> \
{ \
enum { __value = 1 }; \
typedef __true_type __type; \
}; \
template<> \
struct __is_integer<unsigned TYPE> \
{ \
enum { __value = 1 }; \
typedef __true_type __type; \
};
#ifdef __GLIBCXX_TYPE_INT_N_0
__INT_N(__GLIBCXX_TYPE_INT_N_0)
#endif
#ifdef __GLIBCXX_TYPE_INT_N_1
__INT_N(__GLIBCXX_TYPE_INT_N_1)
#endif
#ifdef __GLIBCXX_TYPE_INT_N_2
__INT_N(__GLIBCXX_TYPE_INT_N_2)
#endif
#ifdef __GLIBCXX_TYPE_INT_N_3
__INT_N(__GLIBCXX_TYPE_INT_N_3)
#endif
#undef __INT_N
//
// Floating point types
//
template<typename _Tp>
struct __is_floating
{
enum { __value = 0 };
typedef __false_type __type;
};
// three specializations (float, double and 'long double')
template<>
struct __is_floating<float>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_floating<double>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_floating<long double>
{
enum { __value = 1 };
typedef __true_type __type;
};
//
// Pointer types
//
template<typename _Tp>
struct __is_pointer
{
enum { __value = 0 };
typedef __false_type __type;
};
template<typename _Tp>
struct __is_pointer<_Tp*>
{
enum { __value = 1 };
typedef __true_type __type;
};
//
// An arithmetic type is an integer type or a floating point type
//
template<typename _Tp>
struct __is_arithmetic
: public __traitor<__is_integer<_Tp>, __is_floating<_Tp> >
{ };
//
// A scalar type is an arithmetic type or a pointer type
//
template<typename _Tp>
struct __is_scalar
: public __traitor<__is_arithmetic<_Tp>, __is_pointer<_Tp> >
{ };
//
// For use in std::copy and std::find overloads for streambuf iterators.
//
template<typename _Tp>
struct __is_char
{
enum { __value = 0 };
typedef __false_type __type;
};
template<>
struct __is_char<char>
{
enum { __value = 1 };
typedef __true_type __type;
};
#ifdef _GLIBCXX_USE_WCHAR_T
template<>
struct __is_char<wchar_t>
{
enum { __value = 1 };
typedef __true_type __type;
};
#endif
template<typename _Tp>
struct __is_byte
{
enum { __value = 0 };
typedef __false_type __type;
};
template<>
struct __is_byte<char>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_byte<signed char>
{
enum { __value = 1 };
typedef __true_type __type;
};
template<>
struct __is_byte<unsigned char>
{
enum { __value = 1 };
typedef __true_type __type;
};
//
// Move iterator type
//
template<typename _Tp>
struct __is_move_iterator
{
enum { __value = 0 };
typedef __false_type __type;
};
// Fallback implementation of the function in bits/stl_iterator.h used to
// remove the move_iterator wrapper.
template<typename _Iterator>
inline _Iterator
__miter_base(_Iterator __it)
{ return __it; }
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
} // extern "C++"
#endif //_CPP_TYPE_TRAITS_H
c++config.h
std
ISO C++ entities toplevel namespace is std.