Chris@16: /*=============================================================================
Chris@16:     Copyright (c) 2001-2011 Hartmut Kaiser
Chris@16: 
Chris@16:     Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@16:     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: =============================================================================*/
Chris@16: #if !defined(SPIRIT_ALTERNATIVE_FUNCTION_APRIL_23_2007_1046AM)
Chris@16: #define SPIRIT_ALTERNATIVE_FUNCTION_APRIL_23_2007_1046AM
Chris@16: 
Chris@16: #if defined(_MSC_VER)
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/spirit/home/qi/domain.hpp>
Chris@16: #include <boost/spirit/home/qi/detail/assign_to.hpp>
Chris@16: #include <boost/spirit/home/support/unused.hpp>
Chris@16: #include <boost/spirit/home/qi/detail/attributes.hpp>
Chris@16: #include <boost/variant.hpp>
Chris@16: #include <boost/mpl/bool.hpp>
Chris@16: 
Chris@16: namespace boost { namespace spirit { namespace qi { namespace detail
Chris@16: {
Chris@16:     template <typename Variant, typename Expected>
Chris@16:     struct find_substitute
Chris@16:     {
Chris@16:         // Get the typr from the variant that can be a substitute for Expected.
Chris@16:         // If none is found, just return Expected
Chris@16: 
Chris@16:         typedef Variant variant_type;
Chris@16:         typedef typename variant_type::types types;
Chris@16:         typedef typename mpl::end<types>::type end;
Chris@16: 
Chris@16:         typedef typename
Chris@16:             mpl::find_if<types, is_same<mpl::_1, Expected> >::type
Chris@16:         iter_1;
Chris@16: 
Chris@16:         typedef typename
Chris@16:             mpl::eval_if<
Chris@16:                 is_same<iter_1, end>,
Chris@16:                 mpl::find_if<types, traits::is_substitute<mpl::_1, Expected> >,
Chris@16:                 mpl::identity<iter_1>
Chris@16:             >::type
Chris@16:         iter;
Chris@16: 
Chris@16:         typedef typename
Chris@16:             mpl::eval_if<
Chris@16:                 is_same<iter, end>,
Chris@16:                 mpl::identity<Expected>,
Chris@16:                 mpl::deref<iter>
Chris@16:             >::type
Chris@16:         type;
Chris@16:     };
Chris@16: 
Chris@16:     template <typename Iterator, typename Context, typename Skipper,
Chris@16:         typename Attribute>
Chris@16:     struct alternative_function
Chris@16:     {
Chris@16:         alternative_function(
Chris@16:             Iterator& first_, Iterator const& last_, Context& context_,
Chris@16:             Skipper const& skipper_, Attribute& attr_)
Chris@16:           : first(first_), last(last_), context(context_), skipper(skipper_),
Chris@16:             attr(attr_)
Chris@16:         {
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Component>
Chris@16:         bool call(Component const& component, mpl::true_) const
Chris@16:         {
Chris@16:             // if Attribute is not a variant, then pass it as-is
Chris@16:             return component.parse(first, last, context, skipper, attr);
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Component>
Chris@16:         bool call_optional_or_variant(Component const& component, mpl::true_) const
Chris@16:         {
Chris@16:             // If Attribute is an optional, then create an attribute for the Component
Chris@16:             // with the type optional::value_type. If the expected attribute is unused type,
Chris@16:             // use it instead.
Chris@16:             typedef typename
Chris@16:                 traits::attribute_of<Component, Context, Iterator>::type
Chris@16:             expected_type;
Chris@16: 
Chris@16:             typename mpl::if_<
Chris@16:                 is_same<expected_type, unused_type>,
Chris@16:                 unused_type,
Chris@16:                 typename Attribute::value_type>::type
Chris@16:             val;
Chris@16: 
Chris@16:             if (component.parse(first, last, context, skipper, val))
Chris@16:             {
Chris@16:                 traits::assign_to(val, attr);
Chris@16:                 return true;
Chris@16:             }
Chris@16:             return false;
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Component>
Chris@16:         bool call_variant(Component const& component, mpl::false_) const
Chris@16:         {
Chris@16:             // If Attribute is a variant, then search the variant types for a
Chris@16:             // suitable substitute type.
Chris@16: 
Chris@16:             typename
Chris@16:                 find_substitute<Attribute,
Chris@16:                     typename traits::attribute_of<Component, Context, Iterator>::type
Chris@16:                 >::type
Chris@16:             val;
Chris@16: 
Chris@16:             if (component.parse(first, last, context, skipper, val))
Chris@16:             {
Chris@16:                 traits::assign_to(val, attr);
Chris@16:                 return true;
Chris@16:             }
Chris@16:             return false;
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Component>
Chris@16:         bool call_variant(Component const& component, mpl::true_) const
Chris@16:         {
Chris@16:             // If Attribute is a variant and the expected attribute is
Chris@16:             // the same type (pass the variant as-is).
Chris@16: 
Chris@16:             return component.parse(first, last, context, skipper, attr);
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Component>
Chris@16:         bool call_optional_or_variant(Component const& component, mpl::false_) const
Chris@16:         {
Chris@16:             // Attribute is a variant...
Chris@16: 
Chris@16:             typedef typename
Chris@16:                 traits::attribute_of<Component, Context, Iterator>::type
Chris@16:             expected;
Chris@16:             return call_variant(component,
Chris@16:                 is_same<Attribute, expected>());
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Component>
Chris@16:         bool call(Component const& component, mpl::false_) const
Chris@16:         {
Chris@16:             return call_optional_or_variant(
Chris@16:                 component, spirit::traits::not_is_variant<Attribute, qi::domain>());
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Component>
Chris@16:         bool call_unused(Component const& component, mpl::true_) const
Chris@16:         {
Chris@16:             // return true if the parser succeeds
Chris@16:             return call(component,
Chris@16:                 mpl::and_<
Chris@16:                     spirit::traits::not_is_variant<Attribute, qi::domain>,
Chris@16:                     spirit::traits::not_is_optional<Attribute, qi::domain>
Chris@16:                 >());
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Component>
Chris@16:         bool call_unused(Component const& component, mpl::false_) const
Chris@16:         {
Chris@16:             return component.parse(first, last, context, skipper, unused);
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Component>
Chris@16:         bool operator()(Component const& component) const
Chris@16:         {
Chris@16:             // return true if the parser succeeds
Chris@16:             typedef typename traits::not_is_unused<
Chris@16:                 typename traits::attribute_of<Component, Context, Iterator>::type
Chris@16:             >::type predicate;
Chris@16: 
Chris@16:             return call_unused(component, predicate());
Chris@16:         }
Chris@16: 
Chris@16:         Iterator& first;
Chris@16:         Iterator const& last;
Chris@16:         Context& context;
Chris@16:         Skipper const& skipper;
Chris@16:         Attribute& attr;
Chris@16: 
Chris@16:     private:
Chris@16:         // silence MSVC warning C4512: assignment operator could not be generated
Chris@16:         alternative_function& operator= (alternative_function const&);
Chris@16:     };
Chris@16: 
Chris@16:     template <typename Iterator, typename Context, typename Skipper>
Chris@16:     struct alternative_function<Iterator, Context, Skipper, unused_type const>
Chris@16:     {
Chris@16:         alternative_function(
Chris@16:             Iterator& first_, Iterator const& last_, Context& context_,
Chris@16:             Skipper const& skipper_, unused_type)
Chris@16:           : first(first_), last(last_), context(context_), skipper(skipper_)
Chris@16:         {
Chris@16:         }
Chris@16: 
Chris@16:         template <typename Component>
Chris@101:         bool operator()(Component const& component) const
Chris@16:         {
Chris@16:             // return true if the parser succeeds
Chris@16:             return component.parse(first, last, context, skipper,
Chris@16:                 unused);
Chris@16:         }
Chris@16: 
Chris@16:         Iterator& first;
Chris@16:         Iterator const& last;
Chris@16:         Context& context;
Chris@16:         Skipper const& skipper;
Chris@16: 
Chris@16:     private:
Chris@16:         // silence MSVC warning C4512: assignment operator could not be generated
Chris@16:         alternative_function& operator= (alternative_function const&);
Chris@16:     };
Chris@16: 
Chris@16: }}}}
Chris@16: 
Chris@16: #endif