1 // The -*- C++ -*- type traits classes for internal use in libstdc++
3 // Copyright (C) 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 2, or (at your option)
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // You should have received a copy of the GNU General Public License along
17 // with this library; see the file COPYING. If not, write to the Free
18 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
21 // As a special exception, you may use this file as part of a free software
22 // library without restriction. Specifically, if other files instantiate
23 // templates or use macros or inline functions from this file, or you compile
24 // this file and link it with other files to produce an executable, this
25 // file does not by itself cause the resulting executable to be covered by
26 // the GNU General Public License. This exception does not however
27 // invalidate any other reasons why the executable file might be covered by
28 // the GNU General Public License.
30 // Written by Gabriel Dos Reis <dosreis@cmla.ens-cachan.fr>
32 /** @file cpp_type_traits.h
33 * This is an internal header file, included by other library headers.
34 * You should not attempt to use it directly.
37 #ifndef _CPP_TYPE_TRAITS_H
38 #define _CPP_TYPE_TRAITS_H 1
40 #pragma GCC system_header
43 // This file provides some compile-time information about various types.
44 // These representations were designed, on purpose, to be constant-expressions
45 // and not types as found in <stl/bits/type_traits.h>. In particular, they
46 // can be used in control structures and the optimizer hopefully will do
49 // Why integral expressions, and not functions nor types?
50 // Firstly, these compile-time entities are used as template-arguments
51 // so function return values won't work: We need compile-time entities.
52 // We're left with types and constant integral expressions.
53 // Secondly, from the point of view of ease of use, type-based compile-time
54 // information is -not- *that* convenient. On has to write lots of
55 // overloaded functions and to hope that the compiler will select the right
56 // one. As a net effect, the overall structure isn't very clear at first
58 // Thirdly, partial ordering and overload resolution (of function templates)
59 // is highly costly in terms of compiler-resource. It is a Good Thing to
60 // keep these resource consumption as least as possible.
62 // See valarray_array.h for a case use.
64 // -- Gaby (dosreis@cmla.ens-cachan.fr) 2000-03-06.
67 // NB: g++ can not compile these if declared within the class
69 namespace __gnu_internal
72 typedef char __two[2];
74 template <typename _Tp>
75 __one __test_type (int _Tp::*);
76 template <typename _Tp>
77 __two& __test_type (...);
78 } // namespace __gnu_internal
82 // Compare for equality of types.
83 template<typename, typename>
92 template<typename _Tp>
93 struct __are_same<_Tp, _Tp>
101 // Define a nested type if some predicate holds.
102 template<typename, bool>
107 template<typename _Tp>
108 struct __enable_if<_Tp, true>
113 // Holds if the template-argument is a void type.
114 template<typename _Tp>
124 struct __is_void<void>
135 template<typename _Tp>
144 // Thirteen specializations (yes there are eleven standard integer
145 // types; 'long long' and 'unsigned long long' are supported as
148 struct __is_integer<bool>
157 struct __is_integer<char>
166 struct __is_integer<signed char>
175 struct __is_integer<unsigned char>
183 # ifdef _GLIBCXX_USE_WCHAR_T
185 struct __is_integer<wchar_t>
195 struct __is_integer<short>
204 struct __is_integer<unsigned short>
213 struct __is_integer<int>
222 struct __is_integer<unsigned int>
231 struct __is_integer<long>
240 struct __is_integer<unsigned long>
249 struct __is_integer<long long>
258 struct __is_integer<unsigned long long>
267 // Floating point types
269 template<typename _Tp>
278 // three specializations (float, double and 'long double')
280 struct __is_floating<float>
289 struct __is_floating<double>
298 struct __is_floating<long double>
307 // An arithmetic type is an integer type or a floating point type
309 template<typename _Tp>
310 struct __is_arithmetic
314 _M_type = __is_integer<_Tp>::_M_type || __is_floating<_Tp>::_M_type
319 // A fundamental type is `void' or and arithmetic type
321 template<typename _Tp>
322 struct __is_fundamental
326 _M_type = __is_void<_Tp>::_M_type || __is_arithmetic<_Tp>::_M_type
331 // For the immediate use, the following is a good approximation
333 template<typename _Tp>
338 _M_type = (sizeof(__gnu_internal::__test_type<_Tp>(0))
339 != sizeof(__gnu_internal::__one))
345 #endif //_CPP_TYPE_TRAITS_H