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135 lines
4.8 KiB
135 lines
4.8 KiB
/*============================================================================= |
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Copyright (c) 2001-2011 Joel de Guzman |
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Copyright (c) 2001-2011 Hartmut Kaiser |
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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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=============================================================================*/ |
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#if !defined(SPIRIT_OPTIONAL_MARCH_23_2007_1117PM) |
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#define SPIRIT_OPTIONAL_MARCH_23_2007_1117PM |
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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/support/unused.hpp> |
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#include <boost/spirit/home/qi/detail/attributes.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/spirit/home/support/info.hpp> |
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#include <boost/spirit/home/support/container.hpp> |
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#include <boost/spirit/home/qi/parser.hpp> |
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#include <boost/spirit/home/qi/meta_compiler.hpp> |
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#include <boost/spirit/home/qi/detail/assign_to.hpp> |
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#include <boost/optional.hpp> |
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#include <vector> |
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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<qi::domain, proto::tag::negate> // enables -p |
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: mpl::true_ {}; |
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}} |
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namespace boost { namespace spirit { namespace qi |
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{ |
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template <typename Subject> |
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struct optional : unary_parser<optional<Subject> > |
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{ |
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typedef Subject subject_type; |
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template <typename Context, typename Iterator> |
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struct attribute |
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{ |
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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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typedef typename |
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traits::build_optional< |
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typename traits:: |
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attribute_of<Subject, Context, Iterator>::type |
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>::type |
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type; |
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}; |
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optional(Subject const& subject) |
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: subject(subject) {} |
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template <typename Iterator, typename Context |
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, typename Skipper, typename Attribute> |
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bool parse_impl(Iterator& first, Iterator const& last |
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, Context& context, Skipper const& skipper |
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, Attribute& attr, mpl::false_) const |
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{ |
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// create a local value if Attribute is not unused_type |
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typename spirit::result_of::optional_value<Attribute>::type val = |
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typename spirit::result_of::optional_value<Attribute>::type(); |
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if (subject.parse(first, last, context, skipper, val)) |
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{ |
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// assign the parsed value into our attribute |
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spirit::traits::assign_to(val, attr); |
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} |
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return true; |
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} |
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template <typename Iterator, typename Context |
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, typename Skipper, typename Attribute> |
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bool parse_impl(Iterator& first, Iterator const& last |
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, Context& context, Skipper const& skipper |
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, Attribute& attr, mpl::true_) const |
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{ |
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subject.parse(first, last, context, skipper, attr); |
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return true; |
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} |
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template <typename Iterator, typename Context |
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, typename Skipper, typename Attribute> |
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bool parse(Iterator& first, Iterator const& last |
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, Context& context, Skipper const& skipper |
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, Attribute& attr) const |
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{ |
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typedef typename spirit::result_of::optional_value<Attribute>::type |
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attribute_type; |
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return parse_impl(first, last, context, skipper, attr |
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, traits::is_container<attribute_type>()); |
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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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// Parser 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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}}} |
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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<qi::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<qi::optional<Subject>, Attribute |
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, Context, Iterator> |
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: mpl::true_ {}; |
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}}} |
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#endif
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