boost/boost/type_traits/is_const.hpp

   1
   2 // (C) Copyright Dave Abrahams, Steve Cleary, Beman Dawes, Howard
   3 // Hinnant & John Maddock 2000.  Permission to copy, use, modify,
   4 // sell and distribute this software is granted provided this
   5 // copyright notice appears in all copies. This software is provided
   6 // "as is" without express or implied warranty, and with no claim as
   7 // to its suitability for any purpose.
   8 //
   9 // See http://www.boost.org for most recent version including documentation.
  10
  11 #ifndef BOOST_TT_IS_CONST_HPP_INCLUDED
  12 #define BOOST_TT_IS_CONST_HPP_INCLUDED
  13
  14 #include "boost/config.hpp"
  15
  16 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  17 #   include "boost/type_traits/detail/cv_traits_impl.hpp"
  18 #   ifdef __GNUC__
  19 #       include <boost/type_traits/is_reference.hpp>
  20 #   endif
  21 #else
  22 #   include "boost/type_traits/is_reference.hpp"
  23 #   include "boost/type_traits/is_array.hpp"
  24 #   include "boost/type_traits/detail/yes_no_type.hpp"
  25 #   include "boost/type_traits/detail/false_result.hpp"
  26 #endif
  27
  28 // should be the last #include
  29 #include "boost/type_traits/detail/bool_trait_def.hpp"
  30
  31 namespace boost {
  32
  33 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  34
  35 //* is a type T  declared const - is_const<T>
  36 BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_const,T,::boost::detail::cv_traits_imp<T*>::is_const)
  37 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T&,false)
  38
  39 #if defined(__BORLANDC__)
  40 // these are illegal specialisations; cv-qualifies applied to
  41 // references have no effect according to [8.3.2p1],
  42 // C++ Builder requires them though as it treats cv-qualified
  43 // references as distinct types...
  44 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T& const,false)
  45 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T& volatile,false)
  46 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T& const volatile,false)
  47 #endif
  48
  49 #if defined(__GNUC__) && (__GNUC__ < 3)
  50 // special case for gcc where illegally cv-qualified reference types can be
  51 // generated in some corner cases:
  52 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T const,!(::boost::is_reference<T>::value))
  53 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_const,T volatile const,!(::boost::is_reference<T>::value))
  54 #endif
  55
  56 #else
  57
  58 namespace detail {
  59
  60 using ::boost::type_traits::yes_type;
  61 using ::boost::type_traits::no_type;
  62
  63 yes_type is_const_tester(const volatile void*);
  64 no_type is_const_tester(volatile void *);
  65
  66 template <bool is_ref, bool array>
  67 struct is_const_helper
  68     : ::boost::type_traits::false_result
  69 {
  70 };
  71
  72 template <>
  73 struct is_const_helper<false,false>
  74 {
  75     template <typename T> struct result_
  76     {
  77         static T* t;
  78         BOOST_STATIC_CONSTANT(bool, value = (
  79             sizeof(detail::yes_type) == sizeof(detail::is_const_tester(t))
  80             ));
  81     };
  82 };
  83
  84 template <>
  85 struct is_const_helper<false,true>
  86 {
  87     template <typename T> struct result_
  88     {
  89         static T t;
  90         BOOST_STATIC_CONSTANT(bool, value = (
  91             sizeof(detail::yes_type) == sizeof(detail::is_const_tester(&t))
  92             ));
  93     };
  94 };
  95
  96 template <typename T>
  97 struct is_const_impl
  98     : is_const_helper<
  99           is_reference<T>::value
 100         , is_array<T>::value
 101         >::template result_<T>
 102 {
 103 };
 104
 105 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_const,void,false)
 106 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
 107 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_const,void const,true)
 108 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_const,void volatile,false)
 109 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_const,void const volatile,true)
 110 #endif
 111
 112 } // namespace detail
 113
 114 //* is a type T  declared const - is_const<T>
 115 BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_const,T,::boost::detail::is_const_impl<T>::value)
 116
 117 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
 118
 119 } // namespace boost
 120
 121 #include "boost/type_traits/detail/bool_trait_undef.hpp"
 122
 123 #endif // BOOST_TT_IS_CONST_HPP_INCLUDED
 124