1 2 #ifndef BOOST_MPL_VOID_HPP_INCLUDED 3 #define BOOST_MPL_VOID_HPP_INCLUDED 4 5 // Copyright Aleksey Gurtovoy 2001-2004 6 // 7 // Distributed under the Boost Software License, Version 1.0. 8 // (See accompanying file LICENSE_1_0.txt or copy at 9 // http://www.boost.org/LICENSE_1_0.txt) 10 // 11 // See http://www.boost.org/libs/mpl for documentation. 12 13 // $Id$ 14 // $Date$ 15 // $Revision$ 16 17 #include <boost/mpl/void_fwd.hpp> 18 #include <boost/mpl/bool.hpp> 19 #include <boost/mpl/aux_/na_spec.hpp> 20 #include <boost/mpl/aux_/config/msvc.hpp> 21 #include <boost/mpl/aux_/config/workaround.hpp> 22 23 BOOST_MPL_AUX_ADL_BARRIER_NAMESPACE_OPEN 24 25 // [JDG Feb-4-2003] made void_ a complete type to allow it to be 26 // instantiated so that it can be passed in as an object that can be 27 // used to select an overloaded function. Possible use includes signaling 28 // a zero arity functor evaluation call. 29 struct void_ { typedef void_ type; }; 30 31 BOOST_MPL_AUX_ADL_BARRIER_NAMESPACE_CLOSE 32 33 namespace boost { namespace mpl { 34 35 template< typename T > 36 struct is_void_ 37 : false_ 38 { 39 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) 40 using false_::value; 41 #endif 42 }; 43 44 template<> 45 struct is_void_<void_> 46 : true_ 47 { 48 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) 49 using true_::value; 50 #endif 51 }; 52 53 template< typename T > 54 struct is_not_void_ 55 : true_ 56 { 57 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) 58 using true_::value; 59 #endif 60 }; 61 62 template<> 63 struct is_not_void_<void_> 64 : false_ 65 { 66 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300) 67 using false_::value; 68 #endif 69 }; 70 71 BOOST_MPL_AUX_NA_SPEC(1, is_void_) 72 BOOST_MPL_AUX_NA_SPEC(1, is_not_void_) 73 74 }} 75 76 #endif // BOOST_MPL_VOID_HPP_INCLUDED 77