// 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/iterator.hpp> | |
#include <boost/detail/workaround.hpp> | |
#include <boost/detail/iterator.hpp> | |
#include <boost/iterator/detail/any_conversion_eater.hpp> | |
// should be the last #includes | |
#include <boost/type_traits/detail/bool_trait_def.hpp> | |
#include <boost/iterator/detail/config_def.hpp> | |
#ifndef BOOST_NO_IS_CONVERTIBLE | |
namespace boost { | |
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(Value&); | |
}; | |
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 boost::detail::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 boost::detail::iterator_traits<It>::value_type | |
>::template rebind<It> | |
{}; | |
} // namespace detail | |
// Define the trait with full mpl lambda capability and various broken | |
// compiler workarounds | |
BOOST_TT_AUX_BOOL_TRAIT_DEF1( | |
is_lvalue_iterator,T,::boost::detail::is_readable_lvalue_iterator_impl<T>::value) | |
BOOST_TT_AUX_BOOL_TRAIT_DEF1( | |
is_non_const_lvalue_iterator,T,::boost::detail::is_non_const_lvalue_iterator_impl<T>::value) | |
} // namespace boost | |
#endif | |
#include <boost/iterator/detail/config_undef.hpp> | |
#include <boost/type_traits/detail/bool_trait_undef.hpp> | |
#endif // IS_LVALUE_ITERATOR_DWA2003112_HPP |