92 lines
2.4 KiB
Plaintext
92 lines
2.4 KiB
Plaintext
// Copyright Daniel Wallin, David Abrahams 2005. Use, modification and
|
|
// distribution is subject to the Boost Software License, Version 1.0. (See
|
|
// accompanying file LICENSE_1_0.txt or copy at
|
|
// http://www.boost.org/LICENSE_1_0.txt)
|
|
|
|
#ifndef UNWRAP_CV_REFERENCE_050328_HPP
|
|
#define UNWRAP_CV_REFERENCE_050328_HPP
|
|
|
|
#include <boost/parameter/aux_/yesno.hpp>
|
|
#include <boost/mpl/bool.hpp>
|
|
#include <boost/mpl/identity.hpp>
|
|
#include <boost/mpl/eval_if.hpp>
|
|
|
|
namespace boost { template<class T> class reference_wrapper; }
|
|
|
|
namespace boost { namespace parameter { namespace aux {
|
|
|
|
//
|
|
// reference_wrapper support -- because of the forwarding problem,
|
|
// when passing arguments positionally by non-const reference, we
|
|
// ask users of named parameter interfaces to use ref(x) to wrap
|
|
// them.
|
|
//
|
|
|
|
// is_cv_reference_wrapper returns mpl::true_ if T is of type
|
|
// reference_wrapper<U> cv
|
|
template <class U>
|
|
yes_tag is_cv_reference_wrapper_check(reference_wrapper<U> const volatile*);
|
|
no_tag is_cv_reference_wrapper_check(...);
|
|
|
|
template <class T>
|
|
struct is_cv_reference_wrapper
|
|
{
|
|
BOOST_STATIC_CONSTANT(
|
|
bool, value = (
|
|
sizeof(is_cv_reference_wrapper_check((T*)0)) == sizeof(yes_tag)
|
|
)
|
|
);
|
|
|
|
typedef mpl::bool_<
|
|
#if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
|
|
is_cv_reference_wrapper::
|
|
#endif
|
|
value> type;
|
|
};
|
|
|
|
// Needed for unwrap_cv_reference below. T might be const, so
|
|
// eval_if might fail because of deriving from T const on EDG.
|
|
template <class T>
|
|
struct get_type
|
|
{
|
|
typedef typename T::type type;
|
|
};
|
|
|
|
#if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
|
|
template <class T, class is_reference_wrapper = typename is_cv_reference_wrapper<T>::type>
|
|
struct unwrap_cv_reference
|
|
{
|
|
typedef T type;
|
|
};
|
|
|
|
template <class T>
|
|
struct unwrap_cv_reference<T const, mpl::false_>
|
|
{
|
|
typedef T const type;
|
|
};
|
|
|
|
template <class T>
|
|
struct unwrap_cv_reference<T, mpl::true_>
|
|
: T
|
|
{};
|
|
|
|
#else
|
|
// Produces the unwrapped type to hold a reference to in named<>
|
|
// Can't use boost::unwrap_reference<> here because it
|
|
// doesn't handle the case where T = reference_wrapper<U> cv
|
|
template <class T>
|
|
struct unwrap_cv_reference
|
|
{
|
|
typedef typename mpl::eval_if<
|
|
is_cv_reference_wrapper<T>
|
|
, get_type<T>
|
|
, mpl::identity<T>
|
|
>::type type;
|
|
};
|
|
#endif
|
|
|
|
}}} // namespace boost::parameter::aux
|
|
|
|
#endif // UNWRAP_CV_REFERENCE_050328_HPP
|
|
|