boost/type_traits/is_lvalue_reference.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_lvalue_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_LVALUE_REFERENCE_HPP_INCLUDED
  22 #define BOOST_TT_IS_LVALUE_REFERENCE_HPP_INCLUDED
  23
  24 #include <boost/type_traits/config.hpp>
  25
  26 #ifdef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  27 #   include <boost/type_traits/detail/yes_no_type.hpp>
  28 #   include <boost/type_traits/detail/wrap.hpp>
  29 #endif
  30
  31 // should be the last #include
  32 #include <boost/type_traits/detail/bool_trait_def.hpp>
  33
  34 namespace boost {
  35
  36 #if defined( __CODEGEARC__ )
  37 BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_lvalue_reference,T,__is_reference(T))
  38 #elif !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
  39
  40 BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_lvalue_reference,T,false)
  41 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_lvalue_reference,T&,true)
  42
  43 #if  defined(BOOST_ILLEGAL_CV_REFERENCES)
  44 // these are illegal specialisations; cv-qualifies applied to
  45 // references have no effect according to [8.3.2p1],
  46 // C++ Builder requires them though as it treats cv-qualified
  47 // references as distinct types...
  48 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_lvalue_reference,T& const,true)
  49 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_lvalue_reference,T& volatile,true)
  50 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_lvalue_reference,T& const volatile,true)
  51 #endif
  52
  53 #if defined(__GNUC__) && (__GNUC__ < 3)
  54 // these allow us to work around illegally cv-qualified reference
  55 // types.
  56 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_lvalue_reference,T const ,::boost::is_lvalue_reference<T>::value)
  57 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_lvalue_reference,T volatile ,::boost::is_lvalue_reference<T>::value)
  58 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_1(typename T,is_lvalue_reference,T const volatile ,::boost::is_lvalue_reference<T>::value)
  59 // However, the above specializations confuse gcc 2.96 unless we also
  60 // supply these specializations for array types
  61 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_2(typename T,unsigned long N,is_lvalue_reference,T[N],false)
  62 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_2(typename T,unsigned long N,is_lvalue_reference,const T[N],false)
  63 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_2(typename T,unsigned long N,is_lvalue_reference,volatile T[N],false)
  64 BOOST_TT_AUX_BOOL_TRAIT_PARTIAL_SPEC1_2(typename T,unsigned long N,is_lvalue_reference,const volatile T[N],false)
  65 #endif
  66
  67 #else
  68
  69 #ifdef BOOST_MSVC
  70 #   pragma warning(push)
  71 #   pragma warning(disable: 4181 4097)
  72 #endif
  73
  74 namespace detail {
  75
  76 using ::boost::type_traits::yes_type;
  77 using ::boost::type_traits::no_type;
  78 using ::boost::type_traits::wrap;
  79
  80 template <class T> T&(* is_lvalue_reference_helper1(wrap<T>) )(wrap<T>);
  81 char is_lvalue_reference_helper1(...);
  82
  83 template <class T> no_type is_lvalue_reference_helper2(T&(*)(wrap<T>));
  84 yes_type is_lvalue_reference_helper2(...);
  85
  86 template <typename T>
  87 struct is_lvalue_reference_impl
  88 {
  89     BOOST_STATIC_CONSTANT(
  90         bool, value = sizeof(
  91             ::boost::detail::is_lvalue_reference_helper2(
  92                 ::boost::detail::is_lvalue_reference_helper1(::boost::type_traits::wrap<T>()))) == 1
  93         );
  94 };
  95
  96 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_lvalue_reference,void,false)
  97 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
  98 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_lvalue_reference,void const,false)
  99 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_lvalue_reference,void volatile,false)
 100 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_lvalue_reference,void const volatile,false)
 101 #endif
 102
 103 } // namespace detail
 104
 105 BOOST_TT_AUX_BOOL_TRAIT_DEF1(is_lvalue_reference,T,::boost::detail::is_lvalue_reference_impl<T>::value)
 106
 107 #ifdef BOOST_MSVC
 108 #   pragma warning(pop)
 109 #endif
 110
 111 #endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
 112
 113 } // namespace boost
 114
 115 #include <boost/type_traits/detail/bool_trait_undef.hpp>
 116
 117 #endif // BOOST_TT_IS_REFERENCE_HPP_INCLUDED
 118