211 lines
7.0 KiB
C++
211 lines
7.0 KiB
C++
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/*=============================================================================
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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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#ifndef BOOST_SPIRIT_QI_DETAIL_ALTERNATIVE_FUNCTION_HPP
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#define BOOST_SPIRIT_QI_DETAIL_ALTERNATIVE_FUNCTION_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/qi/domain.hpp>
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#include <boost/spirit/home/qi/detail/assign_to.hpp>
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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/variant.hpp>
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#include <boost/mpl/bool.hpp>
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namespace boost { namespace spirit { namespace qi { namespace detail
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{
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template <typename Variant, typename T>
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struct find_substitute
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{
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// Get the type from the Variant that can be a substitute for T.
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// If none is found, just return T
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typedef Variant variant_type;
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typedef typename variant_type::types types;
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typedef typename mpl::end<types>::type end;
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typedef typename mpl::find<types, T>::type iter_1;
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typedef typename
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mpl::eval_if<
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is_same<iter_1, end>,
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mpl::find_if<types, traits::is_substitute<T, mpl::_1> >,
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mpl::identity<iter_1>
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>::type
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iter;
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typedef typename
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mpl::eval_if<
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is_same<iter, end>,
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mpl::identity<T>,
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mpl::deref<iter>
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>::type
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type;
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};
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template <typename Iterator, typename Context, typename Skipper,
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typename Attribute>
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struct alternative_function
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{
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alternative_function(
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Iterator& first_, Iterator const& last_, Context& context_,
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Skipper const& skipper_, Attribute& attr_)
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: first(first_), last(last_), context(context_), skipper(skipper_),
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attr(attr_)
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{
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}
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template <typename Component>
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bool call(Component const& component, mpl::true_) const
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{
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// if Attribute is not a variant, then pass it as-is
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return component.parse(first, last, context, skipper, attr);
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}
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template <typename Component>
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bool call_optional_or_variant(Component const& component, mpl::true_) const
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{
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// If Attribute is an optional, then create an attribute for the Component
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// with the type optional::value_type. If the expected attribute is unused type,
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// use it instead.
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typedef typename
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traits::attribute_of<Component, Context, Iterator>::type
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expected_type;
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typename mpl::if_<
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is_same<expected_type, unused_type>,
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unused_type,
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typename Attribute::value_type>::type
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val;
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if (component.parse(first, last, context, skipper, val))
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{
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traits::assign_to(val, attr);
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return true;
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}
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return false;
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}
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template <typename Component>
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bool call_variant(Component const& component, mpl::false_) const
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{
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// If Attribute is a variant, then search the variant types for a
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// suitable substitute type.
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typename
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find_substitute<Attribute,
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typename traits::attribute_of<Component, Context, Iterator>::type
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>::type
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val;
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if (component.parse(first, last, context, skipper, val))
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{
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traits::assign_to(val, attr);
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return true;
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}
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return false;
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}
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template <typename Component>
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bool call_variant(Component const& component, mpl::true_) const
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{
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// If Attribute is a variant and the expected attribute is
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// the same type (pass the variant as-is).
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return component.parse(first, last, context, skipper, attr);
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}
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template <typename Component>
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bool call_optional_or_variant(Component const& component, mpl::false_) const
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{
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// Attribute is a variant...
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typedef typename
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traits::attribute_of<Component, Context, Iterator>::type
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expected;
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return call_variant(component,
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is_same<Attribute, expected>());
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}
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template <typename Component>
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bool call(Component const& component, mpl::false_) const
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{
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return call_optional_or_variant(
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component, spirit::traits::not_is_variant<Attribute, qi::domain>());
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}
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template <typename Component>
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bool call_unused(Component const& component, mpl::true_) const
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{
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// return true if the parser succeeds
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return call(component,
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mpl::and_<
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spirit::traits::not_is_variant<Attribute, qi::domain>,
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spirit::traits::not_is_optional<Attribute, qi::domain>
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>());
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}
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template <typename Component>
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bool call_unused(Component const& component, mpl::false_) const
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{
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return component.parse(first, last, context, skipper, unused);
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}
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template <typename Component>
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bool operator()(Component const& component) const
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{
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// return true if the parser succeeds
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typedef typename traits::not_is_unused<
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typename traits::attribute_of<Component, Context, Iterator>::type
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>::type predicate;
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return call_unused(component, predicate());
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}
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Iterator& first;
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Iterator const& last;
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Context& context;
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Skipper const& skipper;
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Attribute& attr;
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// silence MSVC warning C4512: assignment operator could not be generated
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BOOST_DELETED_FUNCTION(alternative_function& operator= (alternative_function const&))
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};
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template <typename Iterator, typename Context, typename Skipper>
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struct alternative_function<Iterator, Context, Skipper, unused_type const>
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{
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alternative_function(
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Iterator& first_, Iterator const& last_, Context& context_,
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Skipper const& skipper_, unused_type)
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: first(first_), last(last_), context(context_), skipper(skipper_)
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{
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}
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template <typename Component>
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bool operator()(Component const& component) const
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{
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// return true if the parser succeeds
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return component.parse(first, last, context, skipper,
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unused);
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}
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Iterator& first;
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Iterator const& last;
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Context& context;
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Skipper const& skipper;
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// silence MSVC warning C4512: assignment operator could not be generated
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BOOST_DELETED_FUNCTION(alternative_function& operator= (alternative_function const&))
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};
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}}}}
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#endif
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