boost/spirit/home/classic/core/composite/alternative.hpp
/*=============================================================================
Copyright (c) 1998-2003 Joel de Guzman
Copyright (c) 2001 Daniel Nuffer
Copyright (c) 2002 Hartmut Kaiser
http://spirit.sourceforge.net/
Distributed under 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)
=============================================================================*/
#if !defined(BOOST_SPIRIT_ALTERNATIVE_HPP)
#define BOOST_SPIRIT_ALTERNATIVE_HPP
#include <boost/spirit/home/classic/namespace.hpp>
#include <boost/spirit/home/classic/core/parser.hpp>
#include <boost/spirit/home/classic/core/primitives/primitives.hpp>
#include <boost/spirit/home/classic/core/composite/composite.hpp>
#include <boost/spirit/home/classic/meta/as_parser.hpp>
namespace boost { namespace spirit {
BOOST_SPIRIT_CLASSIC_NAMESPACE_BEGIN
///////////////////////////////////////////////////////////////////////////
//
// alternative class
//
// Handles expressions of the form:
//
// a | b
//
// where a and b are parsers. The expression returns a composite
// parser that matches a or b. One (not both) of the operands may
// be a literal char, wchar_t or a primitive string char const*,
// wchar_t const*.
//
// The expression is short circuit evaluated. b is never touched
// when a is returns a successful match.
//
///////////////////////////////////////////////////////////////////////////
struct alternative_parser_gen;
#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
#pragma warning(push)
#pragma warning(disable:4512) //assignment operator could not be generated
#endif
template <typename A, typename B>
struct alternative
: public binary<A, B, parser<alternative<A, B> > >
{
typedef alternative<A, B> self_t;
typedef binary_parser_category parser_category_t;
typedef alternative_parser_gen parser_generator_t;
typedef binary<A, B, parser<self_t> > base_t;
alternative(A const& a, B const& b)
: base_t(a, b) {}
template <typename ScannerT>
typename parser_result<self_t, ScannerT>::type
parse(ScannerT const& scan) const
{
typedef typename parser_result<self_t, ScannerT>::type result_t;
typedef typename ScannerT::iterator_t iterator_t;
{ // scope for save
iterator_t save = scan.first;
if (result_t hit = this->left().parse(scan))
return hit;
scan.first = save;
}
return this->right().parse(scan);
}
};
#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
#pragma warning(pop)
#endif
struct alternative_parser_gen
{
template <typename A, typename B>
struct result
{
typedef
alternative<
typename as_parser<A>::type
, typename as_parser<B>::type
>
type;
};
template <typename A, typename B>
static alternative<
typename as_parser<A>::type
, typename as_parser<B>::type
>
generate(A const& a, B const& b)
{
return alternative<BOOST_DEDUCED_TYPENAME as_parser<A>::type,
BOOST_DEDUCED_TYPENAME as_parser<B>::type>
(as_parser<A>::convert(a), as_parser<B>::convert(b));
}
};
template <typename A, typename B>
alternative<A, B>
operator|(parser<A> const& a, parser<B> const& b);
template <typename A>
alternative<A, chlit<char> >
operator|(parser<A> const& a, char b);
template <typename B>
alternative<chlit<char>, B>
operator|(char a, parser<B> const& b);
template <typename A>
alternative<A, strlit<char const*> >
operator|(parser<A> const& a, char const* b);
template <typename B>
alternative<strlit<char const*>, B>
operator|(char const* a, parser<B> const& b);
template <typename A>
alternative<A, chlit<wchar_t> >
operator|(parser<A> const& a, wchar_t b);
template <typename B>
alternative<chlit<wchar_t>, B>
operator|(wchar_t a, parser<B> const& b);
template <typename A>
alternative<A, strlit<wchar_t const*> >
operator|(parser<A> const& a, wchar_t const* b);
template <typename B>
alternative<strlit<wchar_t const*>, B>
operator|(wchar_t const* a, parser<B> const& b);
BOOST_SPIRIT_CLASSIC_NAMESPACE_END
}} // namespace BOOST_SPIRIT_CLASSIC_NS
#endif
#include <boost/spirit/home/classic/core/composite/impl/alternative.ipp>
