boost/boost/type_traits/reference_traits.hpp

   1 //  (C) Copyright David Abrahams Steve Cleary, Beman Dawes, Howard
   2 //  Hinnant & John Maddock 2000-2002.  Permission to copy, use,
   3 //  modify, sell and distribute this software is granted provided this
   4 //  copyright notice appears in all copies. This software is provided
   5 //  "as is" without express or implied warranty, and with no claim as
   6 //  to its suitability for any purpose.
   7 //
   8 //  See http://www.boost.org for most recent version including documentation.
   9 //
  10 #ifndef BOOST_TT_REFERENCE_TRAITS_HPP
  11 # define BOOST_TT_REFERENCE_TRAITS_HPP
  12
  13 # ifndef BOOST_TT_UTILITY_HPP
  14 #  include <boost/type_traits/utility.hpp>
  15 # endif // BOOST_TT_UTILITY_HPP
  16
  17 namespace boost {
  18
  19 /**********************************************
  20  *
  21  * is_reference
  22  *
  23  **********************************************/
  24 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  25 template <typename T> struct is_reference
  26 { BOOST_STATIC_CONSTANT(bool, value = false); };
  27 template <typename T> struct is_reference<T&>
  28 { BOOST_STATIC_CONSTANT(bool, value = true); };
  29 #if defined(__BORLANDC__)
  30 // these are illegal specialisations; cv-qualifies applied to
  31 // references have no effect according to [8.3.2p1],
  32 // C++ Builder requires them though as it treats cv-qualified
  33 // references as distinct types...
  34 template <typename T> struct is_reference<T&const>
  35 { BOOST_STATIC_CONSTANT(bool, value = true); };
  36 template <typename T> struct is_reference<T&volatile>
  37 { BOOST_STATIC_CONSTANT(bool, value = true); };
  38 template <typename T> struct is_reference<T&const volatile>
  39 { BOOST_STATIC_CONSTANT(bool, value = true); };
  40 #endif
  41 #else
  42 # ifdef BOOST_MSVC
  43 #  pragma warning(push)
  44 #  pragma warning(disable: 4181)
  45 #endif // BOOST_MSVC
  46
  47 namespace detail
  48 {
  49   using ::boost::type_traits::yes_type;
  50   using ::boost::type_traits::no_type;
  51   using ::boost::type_traits::wrap;
  52
  53   template <class T> T&(* is_reference_helper1(wrap<T>) )(wrap<T>);
  54   char is_reference_helper1(...);
  55
  56   template <class T> no_type is_reference_helper2(T&(*)(wrap<T>));
  57   yes_type is_reference_helper2(...);
  58 }
  59
  60 template <typename T>
  61 struct is_reference
  62 {
  63     BOOST_STATIC_CONSTANT(
  64         bool, value = sizeof(
  65             ::boost::detail::is_reference_helper2(
  66                 ::boost::detail::is_reference_helper1(::boost::type_traits::wrap<T>()))) == 1
  67         );
  68 };
  69
  70 template <> struct is_reference<void>
  71 {
  72    BOOST_STATIC_CONSTANT(bool, value = false);
  73 };
  74 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
  75 template <> struct is_reference<const void>
  76 { BOOST_STATIC_CONSTANT(bool, value = false); };
  77 template <> struct is_reference<volatile void>
  78 { BOOST_STATIC_CONSTANT(bool, value = false); };
  79 template <> struct is_reference<const volatile void>
  80 { BOOST_STATIC_CONSTANT(bool, value = false); };
  81 #endif
  82
  83 # ifdef BOOST_MSVC
  84 #  pragma warning(pop)
  85 # endif // BOOST_MSVC
  86 #endif
  87
  88 } // namespace boost::type_traits
  89
  90 #endif // BOOST_TT_REFERENCE_TRAITS_HPP