63e88f80
 Hu Chunming
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// 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/integral_constant.hpp>
# include <boost/type_traits/remove_cv.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_
{
// a type returned from operator++ when no increment is found in the
// type's own namespace
struct tag {};
// any soaks up implicit conversions and makes the following
// operator++ less-preferred than any other such operator that
// might be found via ADL.
struct any { template <class T> any(T const&); };
// This is a last-resort operator++ for when none other is found
# if BOOST_WORKAROUND(__GNUC__, == 4) && __GNUC_MINOR__ == 0 && __GNUC_PATCHLEVEL__ == 2
}
namespace is_incrementable_2
{
is_incrementable_::tag operator++(is_incrementable_::any const&);
is_incrementable_::tag operator++(is_incrementable_::any const&,int);
}
using namespace is_incrementable_2;
namespace is_incrementable_
{
# else
tag operator++(any const&);
tag operator++(any const&,int);
# endif
# if BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3202))
# define BOOST_comma(a,b) (a)
# else
// In case an operator++ is found that returns void, we'll use ++x,0
tag operator,(tag,int);
# define BOOST_comma(a,b) (a,b)
# endif
# if defined(BOOST_MSVC)
# pragma warning(push)
# pragma warning(disable:4913) // Warning about operator,
# endif
// 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 impl
{
static typename boost::remove_cv<T>::type& x;
BOOST_STATIC_CONSTANT(
bool
, value = sizeof(is_incrementable_::check_(BOOST_comma(++x,0))) == 1
);
};
template <class T>
struct postfix_impl
{
static typename boost::remove_cv<T>::type& x;
BOOST_STATIC_CONSTANT(
bool
, value = sizeof(is_incrementable_::check_(BOOST_comma(x++,0))) == 1
);
};
# if defined(BOOST_MSVC)
# pragma warning(pop)
# endif
}
# undef BOOST_comma
template<typename T>
struct is_incrementable :
public boost::integral_constant<bool, boost::detail::is_incrementable_::impl<T>::value>
{
};
template<typename T>
struct is_postfix_incrementable :
public boost::integral_constant<bool, boost::detail::is_incrementable_::postfix_impl<T>::value>
{
};
} // namespace detail
} // namespace boost
# include <boost/type_traits/detail/bool_trait_undef.hpp>
#endif // IS_INCREMENTABLE_DWA200415_HPP
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