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Whole document tree                   cpp_type_traits.h Go to the documentation of this file. // The -*- C++ -*- type traits classes for internal use in libstdc++ // Copyright (C) 2000-2001 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, // 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. // Written by Gabriel Dos Reis <dosreis@cmla.ens-cachan.fr> #ifndef _CPP_BITS_CPP_TYPE_TRAITS_H #define _CPP_BITS_CPP_TYPE_TRAITS_H 1 #pragma GCC system_header // // 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 <stl/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. // namespace std { template<typename _Tp> struct __is_void { enum { _M_type = 0 }; }; template<> struct __is_void<void> { enum { _M_type = 1 }; }; // // Integer types // template<typename _Tp> struct __is_integer { enum { _M_type = 0 }; }; // Thirteen specializations (yes there are eleven standard integer // types; 'long long' and 'unsigned long long' are supported as // extensions) template<> struct __is_integer<bool> { enum { _M_type = 1 }; }; template<> struct __is_integer<char> { enum { _M_type = 1 }; }; template<> struct __is_integer<signed char> { enum { _M_type = 1 }; }; template<> struct __is_integer<unsigned char> { enum { _M_type = 1 }; }; # ifdef _GLIBCPP_USE_WCHAR_T template<> struct __is_integer<wchar_t> { enum { _M_type = 1 }; }; # endif template<> struct __is_integer<short> { enum { _M_type = 1 }; }; template<> struct __is_integer<unsigned short> { enum { _M_type = 1 }; }; template<> struct __is_integer<int> { enum { _M_type = 1 }; }; template<> struct __is_integer<unsigned int> { enum { _M_type = 1 }; }; template<> struct __is_integer<long> { enum { _M_type = 1 }; }; template<> struct __is_integer<unsigned long> { enum { _M_type = 1 }; }; template<> struct __is_integer<long long> { enum { _M_type = 1 }; }; template<> struct __is_integer<unsigned long long> { enum { _M_type = 1 }; }; // // Floating point types // template<typename _Tp> struct __is_floating { enum { _M_type = 0 }; }; // three specializations (float, double and 'long double') template<> struct __is_floating<float> { enum { _M_type = 1 }; }; template<> struct __is_floating<double> { enum { _M_type = 1 }; }; template<> struct __is_floating<long double> { enum { _M_type = 1 }; }; // // An arithmetic type is an integer type or a floating point type // template<typename _Tp> struct __is_arithmetic { enum { _M_type = __is_integer<_Tp>::_M_type || __is_floating<_Tp>::_M_type }; }; // // A fundamental type is `void' or and arithmetic type // template<typename _Tp> struct __is_fundamental { enum { _M_type = __is_void<_Tp>::_M_type || __is_arithmetic<_Tp>::_M_type }; }; // // For the immediate use, the following is a good approximation // template<typename _Tp> struct __is_pod { enum { _M_type = __is_fundamental<_Tp>::_M_type }; }; } // namespace std #endif //_CPP_BITS_CPP_TYPE_TRAITS_H