boost/type_traits/is_const.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_CONST_HPP_INCLUDED
  22 #define BOOST_TT_IS_CONST_HPP_INCLUDED
  23
  24 #include <boost/config.hpp>
  25 #include <boost/detail/workaround.hpp>
  26
  27 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  28 #   include <boost/type_traits/detail/cv_traits_impl.hpp>
  29 #   ifdef __GNUC__
  30 #       include <boost/type_traits/is_reference.hpp>
  31 #   endif
  32 #   if BOOST_WORKAROUND(BOOST_MSVC, < 1400)
  33 #       include <boost/type_traits/remove_bounds.hpp>
  34 #   endif
  35 #else
  36 #   include <boost/type_traits/is_reference.hpp>
  37 #   include <boost/type_traits/is_array.hpp>
  38 #   include <boost/type_traits/detail/yes_no_type.hpp>
  39 #   include <boost/type_traits/detail/false_result.hpp>
  40 #endif
  41
  42 // should be the last #include
  43 #include <boost/type_traits/detail/bool_trait_def.hpp>
  44
  45 namespace boost {
  46
  47 #if defined( __CODEGEARC__ )
  48
  49 BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_const,T,__is_const(T))
  50
  51 #elif !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
  52
  53 //* is a type T  declared const - is_const<T>
  54 #if BOOST_WORKAROUND(BOOST_MSVC, < 1400)
  55    BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_const,T,::boost::detail::cv_traits_imp<typename remove_bounds<T>::type*>::is_const)
  56 #else
  57    BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_const,T,::boost::detail::cv_traits_imp<T*>::is_const)
  58 #endif
  59 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T&,false)
  60
  61 #if  defined(BOOST_ILLEGAL_CV_REFERENCES)
  62 // these are illegal specialisations; cv-qualifies applied to
  63 // references have no effect according to [8.3.2p1],
  64 // C++ Builder requires them though as it treats cv-qualified
  65 // references as distinct types...
  66 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T& const,false)
  67 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T& volatile,false)
  68 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T& const volatile,false)
  69 #endif
  70
  71 #if defined(__GNUC__) && (__GNUC__ < 3)
  72 // special case for gcc where illegally cv-qualified reference types can be
  73 // generated in some corner cases:
  74 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T const,!(::boost::is_reference<T>::value))
  75 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T volatile const,!(::boost::is_reference<T>::value))
  76 #endif
  77
  78 #else
  79
  80 namespace detail {
  81
  82 using ::boost::type_traits::yes_type;
  83 using ::boost::type_traits::no_type;
  84
  85 yes_type is_const_tester(const volatile void*);
  86 no_type is_const_tester(volatile void *);
  87
  88 template <bool is_ref, bool array>
  89 struct is_const_helper
  90     : ::boost::type_traits::false_result
  91 {
  92 };
  93
  94 template <>
  95 struct is_const_helper<false,false>
  96 {
  97     template <typename T> struct result_
  98     {
  99         static T* t;
 100         BOOST_STATIC_CONSTANT(bool, value = (
 101             sizeof(detail::yes_type) == sizeof(detail::is_const_tester(t))
 102             ));
 103     };
 104 };
 105
 106 template <>
 107 struct is_const_helper<false,true>
 108 {
 109     template <typename T> struct result_
 110     {
 111         static T t;
 112         BOOST_STATIC_CONSTANT(bool, value = (
 113             sizeof(detail::yes_type) == sizeof(detail::is_const_tester(&t))
 114             ));
 115     };
 116 };
 117
 118 template <typename T>
 119 struct is_const_impl
 120     : is_const_helper<
 121           is_reference<T>::value
 122         , is_array<T>::value
 123         >::template result_<T>
 124 {
 125 };
 126
 127 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_const,void,false)
 128 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
 129 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_const,void const,true)
 130 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_const,void volatile,false)
 131 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_const,void const volatile,true)
 132 #endif
 133
 134 } // namespace detail
 135
 136 //* is a type T  declared const - is_const<T>
 137 BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_const,T,::boost::detail::is_const_impl<T>::value)
 138
 139 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
 140
 141 } // namespace boost
 142
 143 #include <boost/type_traits/detail/bool_trait_undef.hpp>
 144
 145 #endif // BOOST_TT_IS_CONST_HPP_INCLUDED
 146