boost/detail/is_incrementable.hpp
// Copyright David Abrahams 2004. 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_INCREMENTABLE_DWA200415_HPP
# define IS_INCREMENTABLE_DWA200415_HPP
# include <boost/type_traits/remove_cv.hpp>
# include <boost/mpl/bool.hpp>
# include <boost/detail/workaround.hpp>
namespace boost { namespace detail {
// is_incrementable<T> metafunction
//
// Requires: Given x of type T&, if the expression ++x is well-formed
// it must have complete type; otherwise, it must neither be ambiguous
// nor violate access.
// This namespace ensures that ADL doesn't mess things up.
namespace is_incrementable_
{
struct tag {};
// any soaks up implicit conversions and makes the following
// operator++ less-preferred than any other such operator which
// might be found via ADL.
struct any { template <class T> any(T const&); };
tag operator++(any const&);
// two check overloads help us identify which operator++ was picked
char (& check(tag) )[2];
template <class T>
char check(T const&);
template <class T>
struct
# if BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
impl
# else
is_incrementable
# endif
{
static typename remove_cv<T>::type& x;
BOOST_STATIC_CONSTANT(
bool
, value = sizeof(is_incrementable_::check(++x)) == 1
);
typedef mpl::bool_<(
# if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
::boost::detail::is_incrementable_::is_incrementable<T>::
# endif
value)> type;
};
}
# if BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
template <class T>
struct is_incrementable : is_incrementable_::impl<T>
{
};
# else
using is_incrementable_::is_incrementable;
# endif
}} // namespace boost::detail
#endif // IS_INCREMENTABLE_DWA200415_HPP