// Copyright (c) 2001-2011 Joel de Guzman
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// Copyright (c) 2001-2011 Hartmut Kaiser
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_SPIRIT_KARMA_OPERATOR_OPTIONAL_HPP
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#define BOOST_SPIRIT_KARMA_OPERATOR_OPTIONAL_HPP
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#if defined(_MSC_VER)
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#pragma once
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#endif
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#include <boost/spirit/home/karma/domain.hpp>
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#include <boost/spirit/home/karma/generator.hpp>
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#include <boost/spirit/home/karma/meta_compiler.hpp>
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#include <boost/spirit/home/support/info.hpp>
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#include <boost/spirit/home/support/unused.hpp>
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#include <boost/spirit/home/karma/detail/attributes.hpp>
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#include <boost/spirit/home/support/container.hpp>
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#include <boost/spirit/home/support/has_semantic_action.hpp>
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#include <boost/spirit/home/support/handles_container.hpp>
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#include <boost/mpl/assert.hpp>
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#include <boost/optional.hpp>
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#include <boost/proto/operators.hpp>
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#include <boost/proto/tags.hpp>
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#include <boost/type_traits/is_convertible.hpp>
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namespace boost { namespace spirit
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{
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///////////////////////////////////////////////////////////////////////////
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// Enablers
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///////////////////////////////////////////////////////////////////////////
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template <>
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struct use_operator<karma::domain, proto::tag::negate> // enables -g
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: mpl::true_ {};
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}}
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///////////////////////////////////////////////////////////////////////////////
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namespace boost { namespace spirit { namespace karma
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{
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///////////////////////////////////////////////////////////////////////////
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template <typename Subject>
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struct optional : unary_generator<optional<Subject> >
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{
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typedef Subject subject_type;
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typedef typename subject_type::properties properties;
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// Build a boost::optional from the subject's attribute. Note
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// that boost::optional may return unused_type if the
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// subject's attribute is an unused_type.
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template <typename Context, typename Iterator = unused_type>
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struct attribute
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: traits::build_optional<
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typename traits::attribute_of<Subject, Context, Iterator>::type
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>
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{};
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optional(Subject const& subject)
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: subject(subject) {}
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template <
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typename OutputIterator, typename Context, typename Delimiter
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, typename Attribute>
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bool generate(OutputIterator& sink, Context& ctx
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, Delimiter const& d, Attribute const& attr) const
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{
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if (traits::has_optional_value(attr))
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subject.generate(sink, ctx, d, traits::optional_value(attr));
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return sink_is_good(sink);
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}
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template <typename Context>
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info what(Context& context) const
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{
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return info("optional", subject.what(context));
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}
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Subject subject;
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};
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///////////////////////////////////////////////////////////////////////////
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// Generator generators: make_xxx function (objects)
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///////////////////////////////////////////////////////////////////////////
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template <typename Elements, typename Modifiers>
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struct make_composite<proto::tag::negate, Elements, Modifiers>
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: make_unary_composite<Elements, optional> {};
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}}}
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namespace boost { namespace spirit { namespace traits
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{
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///////////////////////////////////////////////////////////////////////////
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template <typename Subject>
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struct has_semantic_action<karma::optional<Subject> >
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: unary_has_semantic_action<Subject> {};
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///////////////////////////////////////////////////////////////////////////
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template <typename Subject, typename Attribute, typename Context
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, typename Iterator>
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struct handles_container<karma::optional<Subject>, Attribute, Context
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, Iterator>
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: mpl::true_ {};
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}}}
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#endif
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