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/*=============================================================================
Copyright (c) 2001-2011 Joel de Guzman
Copyright (c) 2001-2011 Hartmut Kaiser
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_OPTIONAL_MARCH_23_2007_1117PM)
#define SPIRIT_OPTIONAL_MARCH_23_2007_1117PM
#if defined(_MSC_VER)
#pragma once
#endif
#include <boost/spirit/home/support/unused.hpp>
#include <boost/spirit/home/qi/detail/attributes.hpp>
#include <boost/spirit/home/support/has_semantic_action.hpp>
#include <boost/spirit/home/support/handles_container.hpp>
#include <boost/spirit/home/support/info.hpp>
#include <boost/spirit/home/support/container.hpp>
#include <boost/spirit/home/qi/parser.hpp>
#include <boost/spirit/home/qi/meta_compiler.hpp>
#include <boost/spirit/home/qi/detail/assign_to.hpp>
#include <boost/optional.hpp>
#include <vector>
namespace boost { namespace spirit
{
///////////////////////////////////////////////////////////////////////////
// Enablers
///////////////////////////////////////////////////////////////////////////
template <>
struct use_operator<qi::domain, proto::tag::negate> // enables -p
: mpl::true_ {};
}}
namespace boost { namespace spirit { namespace qi
{
template <typename Subject>
struct optional : unary_parser<optional<Subject> >
{
typedef Subject subject_type;
template <typename Context, typename Iterator>
struct attribute
{
// Build a boost::optional from the subject's attribute. Note
// that boost::optional may return unused_type if the
// subject's attribute is an unused_type.
typedef typename
traits::build_optional<
typename traits::
attribute_of<Subject, Context, Iterator>::type
>::type
type;
};
optional(Subject const& subject_)
: subject(subject_) {}
template <typename Iterator, typename Context
, typename Skipper, typename Attribute>
bool parse_impl(Iterator& first, Iterator const& last
, Context& context, Skipper const& skipper
, Attribute& attr_, mpl::false_) const
{
// create a local value if Attribute is not unused_type
typename spirit::result_of::optional_value<Attribute>::type val =
typename spirit::result_of::optional_value<Attribute>::type();
if (subject.parse(first, last, context, skipper, val))
{
// assign the parsed value into our attribute
spirit::traits::assign_to(val, attr_);
}
return true;
}
template <typename Iterator, typename Context
, typename Skipper, typename Attribute>
bool parse_impl(Iterator& first, Iterator const& last
, Context& context, Skipper const& skipper
, Attribute& attr_, mpl::true_) const
{
subject.parse(first, last, context, skipper, attr_);
return true;
}
template <typename Iterator, typename Context
, typename Skipper, typename Attribute>
bool parse(Iterator& first, Iterator const& last
, Context& context, Skipper const& skipper
, Attribute& attr_) const
{
typedef typename spirit::result_of::optional_value<Attribute>::type
attribute_type;
return parse_impl(first, last, context, skipper, attr_
, traits::is_container<attribute_type>());
}
template <typename Context>
info what(Context& context) const
{
return info("optional", subject.what(context));
}
Subject subject;
};
///////////////////////////////////////////////////////////////////////////
// Parser generators: make_xxx function (objects)
///////////////////////////////////////////////////////////////////////////
template <typename Elements, typename Modifiers>
struct make_composite<proto::tag::negate, Elements, Modifiers>
: make_unary_composite<Elements, optional>
{};
}}}
namespace boost { namespace spirit { namespace traits
{
///////////////////////////////////////////////////////////////////////////
template <typename Subject>
struct has_semantic_action<qi::optional<Subject> >
: unary_has_semantic_action<Subject> {};
///////////////////////////////////////////////////////////////////////////
template <typename Subject, typename Attribute, typename Context
, typename Iterator>
struct handles_container<qi::optional<Subject>, Attribute
, Context, Iterator>
: mpl::true_ {};
}}}
#endif
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