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added is_reference_wrapper<>, unwrap_reference<>

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[SVN r12470]
This commit is contained in:
Dave Abrahams 2002-01-23 21:19:14 +00:00
parent c7c09696db
commit f3f697bbc8
1 changed files with 91 additions and 10 deletions
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101
include/boost/ref.hpp
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@ -1,9 +1,9 @@
#ifndef BOOST_REF_HPP_INCLUDED #ifndef BOOST_REF_HPP_INCLUDED
#define BOOST_REF_HPP_INCLUDED # define BOOST_REF_HPP_INCLUDED
#if _MSC_VER+0 >= 1020 # if _MSC_VER+0 >= 1020
#pragma once # pragma once
#endif # endif
// //
// ref.hpp - ref/cref, useful helper functions // ref.hpp - ref/cref, useful helper functions
@ -25,6 +25,7 @@ namespace boost
template<class T> class reference_wrapper template<class T> class reference_wrapper
{ {
public: public:
typedef T type;
explicit reference_wrapper(T & t): t_(t) {} explicit reference_wrapper(T & t): t_(t) {}
@ -39,11 +40,11 @@ private:
reference_wrapper & operator= (reference_wrapper const &); reference_wrapper & operator= (reference_wrapper const &);
}; };
#if defined(__BORLANDC__) && (__BORLANDC__ <= 0x551) # if defined(__BORLANDC__) && (__BORLANDC__ <= 0x551)
#define BOOST_REF_CONST # define BOOST_REF_CONST
#else # else
#define BOOST_REF_CONST const # define BOOST_REF_CONST const
#endif # endif
template<class T> inline reference_wrapper<T> BOOST_REF_CONST ref(T & t) template<class T> inline reference_wrapper<T> BOOST_REF_CONST ref(T & t)
{ {
@ -55,7 +56,87 @@ template<class T> inline reference_wrapper<T const> BOOST_REF_CONST cref(T const
return reference_wrapper<T const>(t); return reference_wrapper<T const>(t);
} }
#undef BOOST_REF_CONST # undef BOOST_REF_CONST
# ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
template<typename T>
class is_reference_wrapper
{
public:
BOOST_STATIC_CONSTANT(bool, value = false);
};
template<typename T>
class is_reference_wrapper<reference_wrapper<T> >
{
public:
BOOST_STATIC_CONSTANT(bool, value = true);
};
template<typename T>
class unwrap_reference
{
public:
typedef T type;
};
template<typename T>
class unwrap_reference<reference_wrapper<T> >
{
public:
typedef T type;
};
# else // no partial specialization
namespace detail
{
typedef char (&yes_reference_wrapper_t)[1];
typedef char (&no_reference_wrapper_t)[2];
no_reference_wrapper_t is_reference_wrapper_test(...);
template<typename T>
yes_reference_wrapper_t is_reference_wrapper_test(reference_wrapper<T>*);
template<bool wrapped>
struct reference_unwrapper
{
template <class T>
struct apply
{
typedef T type;
};
};
template<>
struct reference_unwrapper<true>
{
template <class T>
struct apply
{
typedef typename T::type type;
};
};
}
template<typename T>
class is_reference_wrapper
{
public:
static T* t;
BOOST_STATIC_CONSTANT(
bool, value = (
sizeof(detail::is_reference_wrapper_test(t))
== sizeof(detail::yes_reference_wrapper_t)));
};
template <typename T>
class unwrap_reference
: public detail::reference_unwrapper<
is_reference_wrapper<T>::value
>::template apply<T>
{};
# endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
} // namespace boost } // namespace boost