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// Copyright David Abrahams, Daniel Wallin 2003.
// Distributed under 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 BOOST_PARAMETER_OPTIONAL_HPP
#define BOOST_PARAMETER_OPTIONAL_HPP
#include <boost/parameter/aux_/use_default.hpp>
namespace boost { namespace parameter {
// This metafunction can be used to describe the treatment of particular
// named parameters for the purposes of overload elimination with SFINAE,
// by placing specializations in the parameters<...> list. In order for
// a treated function to participate in overload resolution:
//
// - The actual argument type matched by every keyword tag
// associated with a predicate must satisfy that predicate
//
// - If a keyword k is specified without an optional<...> or
// required<...> wrapper, it is treated as though
// optional<k> were specified.
template <
typename Tag
, typename Predicate = ::boost::parameter::aux::use_default
>
struct optional
{
typedef Tag key_type;
typedef Predicate predicate;
};
}}
#include <boost/parameter/config.hpp>
#if defined(BOOST_PARAMETER_CAN_USE_MP11)
#include <boost/mp11/integral.hpp>
#else
#include <boost/mpl/bool.hpp>
#endif
namespace boost { namespace parameter { namespace aux {
template <typename T>
struct is_optional
#if defined(BOOST_PARAMETER_CAN_USE_MP11)
: ::boost::mp11::mp_false
#else
: ::boost::mpl::false_
#endif
{
};
template <typename Tag, typename Predicate>
struct is_optional< ::boost::parameter::optional<Tag,Predicate> >
#if defined(BOOST_PARAMETER_CAN_USE_MP11)
: ::boost::mp11::mp_true
#else
: ::boost::mpl::true_
#endif
{
};
}}} // namespace boost::parameter::aux
#endif // include guard
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16 entries across 16 versions & 1 rubygems