source: NonGTP/Boost/boost/mpl/has_xxx.hpp @ 857

Revision 857, 7.1 KB checked in by igarcia, 19 years ago (diff)
Line 
1
2#ifndef BOOST_MPL_HAS_XXX_HPP_INCLUDED
3#define BOOST_MPL_HAS_XXX_HPP_INCLUDED
4
5// Copyright Aleksey Gurtovoy 2002-2004
6// Copyright David Abrahams 2002-2003
7//
8// Distributed under the Boost Software License, Version 1.0.
9// (See accompanying file LICENSE_1_0.txt or copy at
10// http://www.boost.org/LICENSE_1_0.txt)
11//
12// See http://www.boost.org/libs/mpl for documentation.
13
14// $Source: /cvsroot/boost/boost/boost/mpl/has_xxx.hpp,v $
15// $Date: 2005/06/15 10:43:23 $
16// $Revision: 1.4 $
17
18#include <boost/mpl/bool.hpp>
19#include <boost/mpl/aux_/type_wrapper.hpp>
20#include <boost/mpl/aux_/yes_no.hpp>
21#include <boost/mpl/aux_/config/has_xxx.hpp>
22#include <boost/mpl/aux_/config/msvc_typename.hpp>
23#include <boost/mpl/aux_/config/msvc.hpp>
24#include <boost/mpl/aux_/config/static_constant.hpp>
25#include <boost/mpl/aux_/config/workaround.hpp>
26
27#include <boost/preprocessor/cat.hpp>
28
29#if !defined(BOOST_MPL_CFG_NO_HAS_XXX)
30
31#   if BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
32
33// agurt, 11/sep/02: MSVC-specific version (< 7.1), based on a USENET
34// newsgroup's posting by John Madsen (comp.lang.c++.moderated,
35// 1999-11-12 19:17:06 GMT); the code is _not_ standard-conforming, but
36// it works way more reliably than the SFINAE-based implementation
37
38// Modified dwa 8/Oct/02 to handle reference types.
39
40#   include <boost/mpl/if.hpp>
41#   include <boost/mpl/bool.hpp>
42
43namespace boost { namespace mpl { namespace aux {
44
45struct has_xxx_tag;
46
47#if BOOST_WORKAROUND(BOOST_MSVC, == 1300)
48template< typename U > struct msvc_incomplete_array
49{
50    typedef char (&type)[sizeof(U) + 1];
51};
52#endif
53
54template< typename T >
55struct msvc_is_incomplete
56{
57    // MSVC is capable of some kinds of SFINAE.  If U is an incomplete
58    // type, it won't pick the second overload
59    static char tester(...);
60
61#if BOOST_WORKAROUND(BOOST_MSVC, == 1300)
62    template< typename U >
63    static typename msvc_incomplete_array<U>::type tester(type_wrapper<U>);
64#else
65    template< typename U >
66    static char (& tester(type_wrapper<U>) )[sizeof(U)+1];
67#endif
68   
69    BOOST_STATIC_CONSTANT(bool, value =
70          sizeof(tester(type_wrapper<T>())) == 1
71        );
72};
73
74template<>
75struct msvc_is_incomplete<int>
76{
77    BOOST_STATIC_CONSTANT(bool, value = false);
78};
79
80}}}
81
82#   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF_(trait, name, default_) \
83template< typename T, typename name = ::boost::mpl::aux::has_xxx_tag > \
84struct BOOST_PP_CAT(trait,_impl) : T \
85{ \
86    static boost::mpl::aux::no_tag \
87    test(void(*)(::boost::mpl::aux::has_xxx_tag)); \
88    \
89    static boost::mpl::aux::yes_tag test(...); \
90    \
91    BOOST_STATIC_CONSTANT(bool, value = \
92          sizeof(test(static_cast<void(*)(name)>(0))) \
93            != sizeof(boost::mpl::aux::no_tag) \
94        ); \
95    typedef boost::mpl::bool_<value> type; \
96}; \
97\
98template< typename T, typename fallback_ = boost::mpl::bool_<default_> > \
99struct trait \
100    : boost::mpl::if_c< \
101          boost::mpl::aux::msvc_is_incomplete<T>::value \
102        , boost::mpl::bool_<false> \
103        , BOOST_PP_CAT(trait,_impl)<T> \
104        >::type \
105{ \
106}; \
107\
108BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, void) \
109BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, bool) \
110BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, char) \
111BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, signed char) \
112BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, unsigned char) \
113BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, signed short) \
114BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, unsigned short) \
115BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, signed int) \
116BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, unsigned int) \
117BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, signed long) \
118BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, unsigned long) \
119BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, float) \
120BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, double) \
121BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, long double) \
122/**/
123
124#   define BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, T) \
125template<> struct trait<T> \
126{ \
127    BOOST_STATIC_CONSTANT(bool, value = false); \
128    typedef boost::mpl::bool_<false> type; \
129}; \
130/**/
131
132#if !defined(BOOST_NO_INTRINSIC_WCHAR_T)
133#   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(trait, name, unused) \
134    BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF_(trait, name, unused) \
135    BOOST_MPL_AUX_HAS_XXX_TRAIT_SPEC(trait, wchar_t) \
136/**/
137#else
138#   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(trait, name, unused) \
139    BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF_(trait, name, unused) \
140/**/
141#endif
142
143
144// SFINAE-based implementations below are derived from a USENET newsgroup's
145// posting by Rani Sharoni (comp.lang.c++.moderated, 2002-03-17 07:45:09 PST)
146
147#   elif BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1400))
148
149// MSVC 7.1+
150
151// agurt, 15/jun/05: replace overload-based SFINAE implementation with SFINAE
152// applied to partial specialization to fix some apparently random failures
153// (thanks to Daniel Wallin for researching this!)
154
155namespace boost { namespace mpl { namespace aux {
156template< typename T > struct msvc71_sfinae_helper { typedef void type; };
157}}}
158
159#   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(trait, name, default_) \
160template< typename T, typename U = void > \
161struct BOOST_PP_CAT(trait,_impl_) \
162{ \
163    BOOST_STATIC_CONSTANT(bool, value = false); \
164    typedef boost::mpl::bool_<value> type; \
165}; \
166\
167template< typename T > \
168struct BOOST_PP_CAT(trait,_impl_)< \
169      T \
170    , typename boost::mpl::aux::msvc71_sfinae_helper< typename T::name >::type \
171    > \
172{ \
173    BOOST_STATIC_CONSTANT(bool, value = true); \
174    typedef boost::mpl::bool_<value> type; \
175}; \
176\
177template< typename T, typename fallback_ = boost::mpl::bool_<default_> > \
178struct trait \
179    : BOOST_PP_CAT(trait,_impl_)<T> \
180{ \
181}; \
182/**/
183
184#   else // other SFINAE-capable compilers
185
186#   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(trait, name, default_) \
187template< typename T, typename fallback_ = boost::mpl::bool_<default_> > \
188struct trait \
189{ \
190    struct gcc_3_2_wknd \
191    { \
192        template< typename U > \
193        static boost::mpl::aux::yes_tag test( \
194              boost::mpl::aux::type_wrapper<U> const volatile* \
195            , boost::mpl::aux::type_wrapper<BOOST_MSVC_TYPENAME U::name>* = 0 \
196            ); \
197    \
198        static boost::mpl::aux::no_tag test(...); \
199    }; \
200    \
201    typedef boost::mpl::aux::type_wrapper<T> t_; \
202    BOOST_STATIC_CONSTANT(bool, value = \
203          sizeof(gcc_3_2_wknd::test(static_cast<t_*>(0))) \
204            == sizeof(boost::mpl::aux::yes_tag) \
205        ); \
206    typedef boost::mpl::bool_<value> type; \
207}; \
208/**/
209
210#   endif // BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
211
212
213#else // BOOST_MPL_CFG_NO_HAS_XXX
214
215// placeholder implementation
216
217#   define BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(trait, name, default_) \
218template< typename T, typename fallback_ = boost::mpl::bool_<default_> > \
219struct trait \
220{ \
221    BOOST_STATIC_CONSTANT(bool, value = fallback_::value); \
222    typedef fallback_ type; \
223}; \
224/**/
225
226#endif
227
228#define BOOST_MPL_HAS_XXX_TRAIT_DEF(name) \
229    BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(BOOST_PP_CAT(has_,name), name, false) \
230/**/
231
232#endif // BOOST_MPL_HAS_XXX_HPP_INCLUDED
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