boost/spirit/home/karma/detail/attributes.hpp
// Copyright (c) 2001-2011 Hartmut Kaiser
// Copyright (c) 2001-2011 Joel de Guzman
//
// 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)
#if !defined(SPIRIT_KARMA_DETAIL_ATTRIBUTES_APR_18_2010_0453PM)
#define SPIRIT_KARMA_DETAIL_ATTRIBUTES_APR_18_2010_0453PM
#include <boost/spirit/home/karma/domain.hpp>
#include <boost/spirit/home/support/attributes_fwd.hpp>
#include <boost/spirit/home/support/attributes.hpp>
///////////////////////////////////////////////////////////////////////////////
namespace boost { namespace spirit { namespace karma
{
template <typename Exposed, typename Transformed, typename Enable = void>
struct transform_attribute
{
typedef Transformed type;
static Transformed pre(Exposed& val)
{
return Transformed(traits::extract_from<Transformed>(val, unused));
}
// Karma only, no post() and no fail() required
};
template <typename Exposed, typename Transformed>
struct transform_attribute<boost::optional<Exposed> const, Transformed
, typename disable_if<is_same<boost::optional<Exposed>, Transformed> >::type>
{
typedef Transformed const& type;
static Transformed const& pre(boost::optional<Exposed> const& val)
{
return boost::get<Transformed>(val);
}
};
template <typename Attribute>
struct transform_attribute<Attribute const, Attribute>
{
typedef Attribute const& type;
static Attribute const& pre(Attribute const& val) { return val; }
// Karma only, no post() and no fail() required
};
// unused_type needs some special handling as well
template <>
struct transform_attribute<unused_type, unused_type>
{
typedef unused_type type;
static unused_type pre(unused_type) { return unused; }
};
template <>
struct transform_attribute<unused_type const, unused_type>
: transform_attribute<unused_type, unused_type>
{};
template <typename Attribute>
struct transform_attribute<Attribute, unused_type>
: transform_attribute<unused_type, unused_type>
{};
template <typename Attribute>
struct transform_attribute<Attribute const, unused_type>
: transform_attribute<unused_type, unused_type>
{};
}}}
///////////////////////////////////////////////////////////////////////////////
namespace boost { namespace spirit { namespace traits { namespace detail
{
template <typename Exposed, typename Transformed>
struct transform_attribute_base<Exposed, Transformed, karma::domain>
: karma::transform_attribute<Exposed, Transformed>
{};
}}}}
#endif