boost/spirit/core/composite/actions.hpp
/*=============================================================================
Copyright (c) 1998-2003 Joel de Guzman
http://spirit.sourceforge.net/
Use, modification and distribution is subject to 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)
=============================================================================*/
#ifndef BOOST_SPIRIT_ACTIONS_HPP
#define BOOST_SPIRIT_ACTIONS_HPP
#include <boost/spirit/core/parser.hpp>
#include <boost/spirit/core/composite/composite.hpp>
namespace boost { namespace spirit {
///////////////////////////////////////////////////////////////////////////
//
// action class
//
// The action class binds a parser with a user defined semantic
// action. Instances of action are never created manually. Instead,
// action objects are typically created indirectly through
// expression templates of the form:
//
// p[f]
//
// where p is a parser and f is a function or functor. The semantic
// action may be a function or a functor. When the parser is
// successful, the actor calls the scanner's action_policy policy
// (see scanner.hpp):
//
// scan.do_action(actor, attribute, first, last);
//
// passing in these information:
//
// actor: The action's function or functor
// attribute: The match (returned by the parser) object's
// attribute (see match.hpp)
// first: Iterator pointing to the start of the matching
// portion of the input
// last: Iterator pointing to one past the end of the
// matching portion of the input
//
// It is the responsibility of the scanner's action_policy policy to
// dispatch the function or functor as it sees fit. The expected
// function or functor signature depends on the parser being
// wrapped. In general, if the attribute type of the parser being
// wrapped is a nil_t, the function or functor expect the signature:
//
// void func(Iterator first, Iterator last); // functions
//
// struct ftor // functors
// {
// void func(Iterator first, Iterator last) const;
// };
//
// where Iterator is the type of the iterator that is being used and
// first and last are the iterators pointing to the matching portion
// of the input.
//
// If the attribute type of the parser being wrapped is not a nil_t,
// the function or functor usually expect the signature:
//
// void func(T val); // functions
//
// struct ftor // functors
// {
// void func(T val) const;
// };
//
// where T is the attribute type and val is the attribute value
// returned by the parser being wrapped.
//
///////////////////////////////////////////////////////////////////////////
template <typename ParserT, typename ActionT>
class action : public unary<ParserT, parser<action<ParserT, ActionT> > >
{
public:
typedef action<ParserT, ActionT> self_t;
typedef action_parser_category parser_category_t;
typedef unary<ParserT, parser<self_t> > base_t;
typedef ActionT predicate_t;
template <typename ScannerT>
struct result
{
typedef typename parser_result<ParserT, ScannerT>::type type;
};
action(ParserT const& p, ActionT const& a)
: base_t(p)
, actor(a) {}
template <typename ScannerT>
typename parser_result<self_t, ScannerT>::type
parse(ScannerT const& scan) const
{
typedef typename ScannerT::iterator_t iterator_t;
typedef typename parser_result<self_t, ScannerT>::type result_t;
scan.at_end(); // allow skipper to take effect
iterator_t save = scan.first;
result_t hit = this->subject().parse(scan);
if (hit)
{
typename result_t::return_t val = hit.value();
scan.do_action(actor, val, save, scan.first);
}
return hit;
}
ActionT const& predicate() const { return actor; }
private:
ActionT actor;
};
}} // namespace boost::spirit
#endif
