libstdc++
type_traits.h
Go to the documentation of this file.
00001 // -*- C++ -*-
00002 
00003 // Copyright (C) 2005, 2006, 2007, 2009 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 3, 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 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /** @file ext/type_traits.h
00026  *  This file is a GNU extension to the Standard C++ Library.
00027  */
00028 
00029 #ifndef _EXT_TYPE_TRAITS
00030 #define _EXT_TYPE_TRAITS 1
00031 
00032 #pragma GCC system_header
00033 
00034 #include <bits/c++config.h>
00035 #include <bits/cpp_type_traits.h>
00036 
00037 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
00038 {
00039 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00040 
00041   // Define a nested type if some predicate holds.
00042   template<bool, typename>
00043     struct __enable_if 
00044     { };
00045 
00046   template<typename _Tp>
00047     struct __enable_if<true, _Tp>
00048     { typedef _Tp __type; };
00049 
00050 
00051   // Conditional expression for types. If true, first, if false, second.
00052   template<bool _Cond, typename _Iftrue, typename _Iffalse>
00053     struct __conditional_type
00054     { typedef _Iftrue __type; };
00055 
00056   template<typename _Iftrue, typename _Iffalse>
00057     struct __conditional_type<false, _Iftrue, _Iffalse>
00058     { typedef _Iffalse __type; };
00059 
00060 
00061   // Given an integral builtin type, return the corresponding unsigned type.
00062   template<typename _Tp>
00063     struct __add_unsigned
00064     { 
00065     private:
00066       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
00067       
00068     public:
00069       typedef typename __if_type::__type __type; 
00070     };
00071 
00072   template<>
00073     struct __add_unsigned<char>
00074     { typedef unsigned char __type; };
00075 
00076   template<>
00077     struct __add_unsigned<signed char>
00078     { typedef unsigned char __type; };
00079 
00080   template<>
00081     struct __add_unsigned<short>
00082     { typedef unsigned short __type; };
00083 
00084   template<>
00085     struct __add_unsigned<int>
00086     { typedef unsigned int __type; };
00087 
00088   template<>
00089     struct __add_unsigned<long>
00090     { typedef unsigned long __type; };
00091 
00092   template<>
00093     struct __add_unsigned<long long>
00094     { typedef unsigned long long __type; };
00095 
00096   // Declare but don't define.
00097   template<>
00098     struct __add_unsigned<bool>;
00099 
00100   template<>
00101     struct __add_unsigned<wchar_t>;
00102 
00103 
00104   // Given an integral builtin type, return the corresponding signed type.
00105   template<typename _Tp>
00106     struct __remove_unsigned
00107     { 
00108     private:
00109       typedef __enable_if<std::__is_integer<_Tp>::__value, _Tp> __if_type;
00110       
00111     public:
00112       typedef typename __if_type::__type __type; 
00113     };
00114 
00115   template<>
00116     struct __remove_unsigned<char>
00117     { typedef signed char __type; };
00118 
00119   template<>
00120     struct __remove_unsigned<unsigned char>
00121     { typedef signed char __type; };
00122 
00123   template<>
00124     struct __remove_unsigned<unsigned short>
00125     { typedef short __type; };
00126 
00127   template<>
00128     struct __remove_unsigned<unsigned int>
00129     { typedef int __type; };
00130 
00131   template<>
00132     struct __remove_unsigned<unsigned long>
00133     { typedef long __type; };
00134 
00135   template<>
00136     struct __remove_unsigned<unsigned long long>
00137     { typedef long long __type; };
00138 
00139   // Declare but don't define.
00140   template<>
00141     struct __remove_unsigned<bool>;
00142 
00143   template<>
00144     struct __remove_unsigned<wchar_t>;
00145 
00146 
00147   // For use in string and vstring.
00148   template<typename _Type>
00149     inline bool
00150     __is_null_pointer(_Type* __ptr)
00151     { return __ptr == 0; }
00152 
00153   template<typename _Type>
00154     inline bool
00155     __is_null_pointer(_Type)
00156     { return false; }
00157 
00158 
00159   // For complex and cmath
00160   template<typename _Tp, bool = std::__is_integer<_Tp>::__value>
00161     struct __promote
00162     { typedef double __type; };
00163 
00164   template<typename _Tp>
00165     struct __promote<_Tp, false>
00166     { typedef _Tp __type; };
00167 
00168   template<typename _Tp, typename _Up>
00169     struct __promote_2
00170     {
00171     private:
00172       typedef typename __promote<_Tp>::__type __type1;
00173       typedef typename __promote<_Up>::__type __type2;
00174 
00175     public:
00176       typedef __typeof__(__type1() + __type2()) __type;
00177     };
00178 
00179   template<typename _Tp, typename _Up, typename _Vp>
00180     struct __promote_3
00181     {
00182     private:
00183       typedef typename __promote<_Tp>::__type __type1;
00184       typedef typename __promote<_Up>::__type __type2;
00185       typedef typename __promote<_Vp>::__type __type3;
00186 
00187     public:
00188       typedef __typeof__(__type1() + __type2() + __type3()) __type;
00189     };
00190 
00191   template<typename _Tp, typename _Up, typename _Vp, typename _Wp>
00192     struct __promote_4
00193     {
00194     private:
00195       typedef typename __promote<_Tp>::__type __type1;
00196       typedef typename __promote<_Up>::__type __type2;
00197       typedef typename __promote<_Vp>::__type __type3;
00198       typedef typename __promote<_Wp>::__type __type4;
00199 
00200     public:
00201       typedef __typeof__(__type1() + __type2() + __type3() + __type4()) __type;
00202     };
00203 
00204 _GLIBCXX_END_NAMESPACE_VERSION
00205 } // namespace
00206 
00207 #endif