boost/spirit/core/composite/difference.hpp
/*=============================================================================
Copyright (c) 1998-2003 Joel de Guzman
Copyright (c) 2001 Daniel Nuffer
Copyright (c) 2002 Hartmut Kaiser
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)
=============================================================================*/
#if !defined(BOOST_SPIRIT_DIFFERENCE_HPP)
#define BOOST_SPIRIT_DIFFERENCE_HPP
#include <boost/spirit/core/parser.hpp>
#include <boost/spirit/core/primitives/primitives.hpp>
#include <boost/spirit/core/composite/composite.hpp>
#include <boost/spirit/meta/as_parser.hpp>
namespace boost { namespace spirit {
///////////////////////////////////////////////////////////////////////////
//
// difference: a - b; Matches a but not b
//
// Handles expressions of the form:
//
// a - b
//
// where a and b are parsers. The expression returns a composite
// parser that matches a but not b. One (not both) of the operands
// may be a literal char, wchar_t or a primitive string char const*,
// wchar_t const*.
//
///////////////////////////////////////////////////////////////////////////
struct difference_parser_gen;
template <typename A, typename B>
struct difference
: public binary<A, B, parser<difference<A, B> > >
{
typedef difference<A, B> self_t;
typedef binary_parser_category parser_category_t;
typedef difference_parser_gen parser_generator_t;
typedef binary<A, B, parser<self_t> > base_t;
difference(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;
iterator_t save = scan.first;
if (result_t hl = this->left().parse(scan))
{
std::swap(save, scan.first);
result_t hr = this->right().parse(scan);
if (!hr || (hr.length() < hl.length()))
{
scan.first = save;
return hl;
}
}
return scan.no_match();
}
};
struct difference_parser_gen
{
template <typename A, typename B>
struct result
{
typedef
difference<
typename as_parser<A>::type
, typename as_parser<B>::type
>
type;
};
template <typename A, typename B>
static difference<
typename as_parser<A>::type
, typename as_parser<B>::type
>
generate(A const& a, B const& b)
{
return difference<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>
difference<A, B>
operator-(parser<A> const& a, parser<B> const& b);
template <typename A>
difference<A, chlit<char> >
operator-(parser<A> const& a, char b);
template <typename B>
difference<chlit<char>, B>
operator-(char a, parser<B> const& b);
template <typename A>
difference<A, strlit<char const*> >
operator-(parser<A> const& a, char const* b);
template <typename B>
difference<strlit<char const*>, B>
operator-(char const* a, parser<B> const& b);
template <typename A>
difference<A, chlit<wchar_t> >
operator-(parser<A> const& a, wchar_t b);
template <typename B>
difference<chlit<wchar_t>, B>
operator-(wchar_t a, parser<B> const& b);
template <typename A>
difference<A, strlit<wchar_t const*> >
operator-(parser<A> const& a, wchar_t const* b);
template <typename B>
difference<strlit<wchar_t const*>, B>
operator-(wchar_t const* a, parser<B> const& b);
}} // namespace boost::spirit
#endif
#include <boost/spirit/core/composite/impl/difference.ipp>
