type_traits.h

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00001 // -*- C++ -*-
00002 
00003 // Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the terms
00007 // of the GNU General Public License as published by the Free Software
00008 // Foundation; either version 2, or (at your option) any later
00009 // version.
00010 
00011 // This library is distributed in the hope that it will be useful, but
00012 // WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014 // General Public License for more details.
00015 
00016 // You should have received a copy of the GNU General Public License along
00017 // with this library; see the file COPYING.  If not, write to the Free
00018 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
00019 // USA.
00020 
00021 // As a special exception, you may use this file as part of a free
00022 // software library without restriction.  Specifically, if other files
00023 // instantiate templates or use macros or inline functions from this
00024 // file, or you compile this file and link it with other files to
00025 // produce an executable, this file does not by itself cause the
00026 // resulting executable to be covered by the GNU General Public
00027 // License.  This exception does not however invalidate any other
00028 // reasons why the executable file might be covered by the GNU General
00029 // Public License.
00030 
00031 /** @file ext/type_traits.h
00032  *  This file is a GNU extension to the Standard C++ Library.
00033  */
00034 
00035 #ifndef _EXT_TYPE_TRAITS
00036 #define _EXT_TYPE_TRAITS 1
00037 
00038 #pragma GCC system_header
00039 
00040 #include <cstddef>
00041 #include <utility>
00042 #include <bits/cpp_type_traits.h>
00043 
00044 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
00045 
00046   // Define a nested type if some predicate holds.
00047   template<bool, typename>
00048     struct __enable_if 
00049     { };
00050 
00051   template<typename _Tp>
00052     struct __enable_if<true, _Tp>
00053     { typedef _Tp __type; };
00054 
00055 
00056   // Conditional expression for types. If true, first, if false, second.
00057   template<bool _Cond, typename _Iftrue, typename _Iffalse>
00058     struct __conditional_type
00059     { typedef _Iftrue __type; };
00060 
00061   template<typename _Iftrue, typename _Iffalse>
00062     struct __conditional_type<false, _Iftrue, _Iffalse>
00063     { typedef _Iffalse __type; };
00064 
00065 
00066   // Given an integral builtin type, return the corresponding unsigned type.
00067   template<typename _Tp>
00068     struct __add_unsigned
00069     { 
00070     private:
00071       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
00072       
00073     public:
00074       typedef typename __if_type::__type __type; 
00075     };
00076 
00077   template<>
00078     struct __add_unsigned<char>
00079     { typedef unsigned char __type; };
00080 
00081   template<>
00082     struct __add_unsigned<signed char>
00083     { typedef unsigned char __type; };
00084 
00085   template<>
00086     struct __add_unsigned<short>
00087     { typedef unsigned short __type; };
00088 
00089   template<>
00090     struct __add_unsigned<int>
00091     { typedef unsigned int __type; };
00092 
00093   template<>
00094     struct __add_unsigned<long>
00095     { typedef unsigned long __type; };
00096 
00097   template<>
00098     struct __add_unsigned<long long>
00099     { typedef unsigned long long __type; };
00100 
00101   // Declare but don't define.
00102   template<>
00103     struct __add_unsigned<bool>;
00104 
00105   template<>
00106     struct __add_unsigned<wchar_t>;
00107 
00108 
00109   // Given an integral builtin type, return the corresponding signed type.
00110   template<typename _Tp>
00111     struct __remove_unsigned
00112     { 
00113     private:
00114       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
00115       
00116     public:
00117       typedef typename __if_type::__type __type; 
00118     };
00119 
00120   template<>
00121     struct __remove_unsigned<char>
00122     { typedef signed char __type; };
00123 
00124   template<>
00125     struct __remove_unsigned<unsigned char>
00126     { typedef signed char __type; };
00127 
00128   template<>
00129     struct __remove_unsigned<unsigned short>
00130     { typedef short __type; };
00131 
00132   template<>
00133     struct __remove_unsigned<unsigned int>
00134     { typedef int __type; };
00135 
00136   template<>
00137     struct __remove_unsigned<unsigned long>
00138     { typedef long __type; };
00139 
00140   template<>
00141     struct __remove_unsigned<unsigned long long>
00142     { typedef long long __type; };
00143 
00144   // Declare but don't define.
00145   template<>
00146     struct __remove_unsigned<bool>;
00147 
00148   template<>
00149     struct __remove_unsigned<wchar_t>;
00150 
00151 _GLIBCXX_END_NAMESPACE
00152 
00153 #endif 

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