// Copyright David Abrahams 2003. 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 IS_LVALUE_ITERATOR_DWA2003112_HPP
|
# define IS_LVALUE_ITERATOR_DWA2003112_HPP
|
|
#include <boost/detail/workaround.hpp>
|
|
#include <boost/type_traits/add_lvalue_reference.hpp>
|
#include <boost/iterator/detail/any_conversion_eater.hpp>
|
#include <boost/mpl/bool.hpp>
|
#include <boost/mpl/aux_/lambda_support.hpp>
|
|
#include <iterator>
|
|
// should be the last #includes
|
#include <boost/type_traits/integral_constant.hpp>
|
#include <boost/iterator/detail/config_def.hpp>
|
|
#ifndef BOOST_NO_IS_CONVERTIBLE
|
|
namespace boost {
|
|
namespace iterators {
|
|
namespace detail
|
{
|
#ifndef BOOST_NO_LVALUE_RETURN_DETECTION
|
// Calling lvalue_preserver( <expression>, 0 ) returns a reference
|
// to the expression's result if <expression> is an lvalue, or
|
// not_an_lvalue() otherwise.
|
struct not_an_lvalue {};
|
|
template <class T>
|
T& lvalue_preserver(T&, int);
|
|
template <class U>
|
not_an_lvalue lvalue_preserver(U const&, ...);
|
|
# define BOOST_LVALUE_PRESERVER(expr) detail::lvalue_preserver(expr,0)
|
|
#else
|
|
# define BOOST_LVALUE_PRESERVER(expr) expr
|
|
#endif
|
|
// Guts of is_lvalue_iterator. Value is the iterator's value_type
|
// and the result is computed in the nested rebind template.
|
template <class Value>
|
struct is_lvalue_iterator_impl
|
{
|
// Eat implicit conversions so we don't report true for things
|
// convertible to Value const&
|
struct conversion_eater
|
{
|
conversion_eater(typename add_lvalue_reference<Value>::type);
|
};
|
|
static char tester(conversion_eater, int);
|
static char (& tester(any_conversion_eater, ...) )[2];
|
|
template <class It>
|
struct rebind
|
{
|
static It& x;
|
|
BOOST_STATIC_CONSTANT(
|
bool
|
, value = (
|
sizeof(
|
is_lvalue_iterator_impl<Value>::tester(
|
BOOST_LVALUE_PRESERVER(*x), 0
|
)
|
) == 1
|
)
|
);
|
};
|
};
|
|
#undef BOOST_LVALUE_PRESERVER
|
|
//
|
// void specializations to handle std input and output iterators
|
//
|
template <>
|
struct is_lvalue_iterator_impl<void>
|
{
|
template <class It>
|
struct rebind : boost::mpl::false_
|
{};
|
};
|
|
#ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
|
template <>
|
struct is_lvalue_iterator_impl<const void>
|
{
|
template <class It>
|
struct rebind : boost::mpl::false_
|
{};
|
};
|
|
template <>
|
struct is_lvalue_iterator_impl<volatile void>
|
{
|
template <class It>
|
struct rebind : boost::mpl::false_
|
{};
|
};
|
|
template <>
|
struct is_lvalue_iterator_impl<const volatile void>
|
{
|
template <class It>
|
struct rebind : boost::mpl::false_
|
{};
|
};
|
#endif
|
|
//
|
// This level of dispatching is required for Borland. We might save
|
// an instantiation by removing it for others.
|
//
|
template <class It>
|
struct is_readable_lvalue_iterator_impl
|
: is_lvalue_iterator_impl<
|
BOOST_DEDUCED_TYPENAME std::iterator_traits<It>::value_type const
|
>::template rebind<It>
|
{};
|
|
template <class It>
|
struct is_non_const_lvalue_iterator_impl
|
: is_lvalue_iterator_impl<
|
BOOST_DEDUCED_TYPENAME std::iterator_traits<It>::value_type
|
>::template rebind<It>
|
{};
|
} // namespace detail
|
|
template< typename T > struct is_lvalue_iterator
|
: public ::boost::integral_constant<bool,::boost::iterators::detail::is_readable_lvalue_iterator_impl<T>::value>
|
{
|
public:
|
BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_lvalue_iterator,(T))
|
};
|
|
template< typename T > struct is_non_const_lvalue_iterator
|
: public ::boost::integral_constant<bool,::boost::iterators::detail::is_non_const_lvalue_iterator_impl<T>::value>
|
{
|
public:
|
BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_non_const_lvalue_iterator,(T))
|
};
|
|
} // namespace iterators
|
|
using iterators::is_lvalue_iterator;
|
using iterators::is_non_const_lvalue_iterator;
|
|
} // namespace boost
|
|
#endif
|
|
#include <boost/iterator/detail/config_undef.hpp>
|
|
#endif // IS_LVALUE_ITERATOR_DWA2003112_HPP
|
