boost/type_traits/is_same.hpp

   1
   2 //  (C) Copyright Dave Abrahams, Steve Cleary, Beman Dawes,
   3 //      Howard Hinnant and John Maddock 2000.
   4 //  (C) Copyright Mat Marcus, Jesse Jones and Adobe Systems Inc 2001
   5
   6 //  Use, modification and distribution are subject to the Boost Software License,
   7 //  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   8 //  http://www.boost.org/LICENSE_1_0.txt).
   9 //
  10 //  See http://www.boost.org/libs/type_traits for most recent version including documentation.
  11
  12 //    Fixed is_pointer, is_reference, is_const, is_volatile, is_same,
  13 //    is_member_pointer based on the Simulated Partial Specialization work
  14 //    of Mat Marcus and Jesse Jones. See  http://opensource.adobe.com or
  15 //    http://groups.yahoo.com/group/boost/message/5441
  16 //    Some workarounds in here use ideas suggested from "Generic<Programming>:
  17 //    Mappings between Types and Values"
  18 //    by Andrei Alexandrescu (see http://www.cuj.com/experts/1810/alexandr.html).
  19
  20
  21 #ifndef BOOST_TT_IS_SAME_HPP_INCLUDED
  22 #define BOOST_TT_IS_SAME_HPP_INCLUDED
  23
  24 #include <boost/type_traits/config.hpp>
  25 #ifdef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  26 #include <boost/type_traits/detail/yes_no_type.hpp>
  27 #include <boost/type_traits/detail/ice_and.hpp>
  28 #include <boost/type_traits/is_reference.hpp>
  29 #endif
  30 // should be the last #include
  31 #include <boost/type_traits/detail/bool_trait_def.hpp>
  32
  33 namespace boost {
  34
  35 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  36
  37 BOOST_TT_AUX_BOOL_TRAIT_DEF2(is_same,T,U,false)
  38 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC2_1(typename T,is_same,T,T,true)
  39 #if BOOST_WORKAROUND(__BORLANDC__, < 0x600)
  40 // without this, Borland's compiler gives the wrong answer for
  41 // references to arrays:
  42 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC2_1(typename T,is_same,T&,T&,true)
  43 #endif
  44
  45 #else // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  46
  47 namespace detail {
  48
  49 #ifdef BOOST_MSVC
  50 // the following VC6 specific implementation is *NOT* legal
  51 // C++, but has the advantage that it works for incomplete
  52 // types.
  53
  54 template< typename T1 >
  55 struct is_same_part_1
  56 {
  57     template<typename T2>  struct part_2     { enum { value = false }; };
  58     template<>             struct part_2<T1> { enum { value = true }; };
  59 };
  60
  61 template< typename T1, typename T2 >
  62 struct is_same_impl
  63 {
  64     enum { value = detail::is_same_part_1<T1>::template part_2<T2>::value };
  65 };
  66
  67 #else // generic "no-partial-specialization" version
  68
  69 template <typename T>
  70 ::boost::type_traits::yes_type
  71 BOOST_TT_DECL is_same_tester(T*, T*);
  72
  73 ::boost::type_traits::no_type
  74 BOOST_TT_DECL is_same_tester(...);
  75
  76 template <typename T, typename U>
  77 struct is_same_impl
  78 {
  79    static T t;
  80    static U u;
  81
  82    BOOST_STATIC_CONSTANT(bool, value =
  83       (::boost::type_traits::ice_and<
  84          (sizeof(type_traits::yes_type) == sizeof(detail::is_same_tester(&t,&u))),
  85          (::boost::is_reference<T>::value == ::boost::is_reference<U>::value),
  86          (sizeof(T) == sizeof(U))
  87         >::value));
  88 };
  89
  90 #endif // BOOST_MSVC
  91
  92 } // namespace detail
  93
  94 BOOST_TT_AUX_BOOL_TRAIT_DEF2(is_same,T,U,(::boost::detail::is_same_impl<T,U>::value))
  95
  96 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  97
  98 } // namespace boost
  99
 100 #include <boost/type_traits/detail/bool_trait_undef.hpp>
 101
 102 #endif  // BOOST_TT_IS_SAME_HPP_INCLUDED
 103