277 lines
9.7 KiB
Plaintext
277 lines
9.7 KiB
Plaintext
/*=============================================================================
|
|
Copyright (c) 1998-2003 Joel de Guzman
|
|
Copyright (c) 2002-2003 Martin Wille
|
|
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)
|
|
=============================================================================*/
|
|
#ifndef BOOST_SPIRIT_EPSILON_HPP
|
|
#define BOOST_SPIRIT_EPSILON_HPP
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
#include <boost/spirit/home/classic/namespace.hpp>
|
|
#include <boost/spirit/home/classic/core/parser.hpp>
|
|
#include <boost/spirit/home/classic/meta/parser_traits.hpp>
|
|
#include <boost/spirit/home/classic/core/composite/composite.hpp>
|
|
#include <boost/spirit/home/classic/core/composite/no_actions.hpp>
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
namespace boost { namespace spirit {
|
|
|
|
BOOST_SPIRIT_CLASSIC_NAMESPACE_BEGIN
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
//
|
|
// condition_parser class
|
|
//
|
|
// handles expresions of the form
|
|
//
|
|
// epsilon_p(cond)
|
|
//
|
|
// where cond is a function or a functor that returns a value suitable
|
|
// to be used in boolean context. The expression returns a parser that
|
|
// returns an empty match when the condition evaluates to true.
|
|
//
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
template <typename CondT, bool positive_ = true>
|
|
struct condition_parser : parser<condition_parser<CondT, positive_> >
|
|
{
|
|
typedef condition_parser<CondT, positive_> self_t;
|
|
|
|
// not explicit! (needed for implementation of if_p et al.)
|
|
condition_parser(CondT const& cond_) : cond(cond_) {}
|
|
|
|
template <typename ScannerT>
|
|
typename parser_result<self_t, ScannerT>::type
|
|
parse(ScannerT const& scan) const
|
|
{
|
|
if (positive_ == bool(cond())) // allow cond to return int
|
|
return scan.empty_match();
|
|
else
|
|
return scan.no_match();
|
|
}
|
|
|
|
condition_parser<CondT, !positive_>
|
|
negate() const
|
|
{ return condition_parser<CondT, !positive_>(cond); }
|
|
|
|
private:
|
|
|
|
CondT cond;
|
|
};
|
|
|
|
#if BOOST_WORKAROUND(BOOST_MSVC, == 1310) || \
|
|
BOOST_WORKAROUND(BOOST_MSVC, == 1400) || \
|
|
BOOST_WORKAROUND(__SUNPRO_CC, <= 0x580)
|
|
// VC 7.1, VC8 and Sun CC <= 5.8 do not support general
|
|
// expressions of non-type template parameters in instantiations
|
|
template <typename CondT>
|
|
inline condition_parser<CondT, false>
|
|
operator~(condition_parser<CondT, true> const& p)
|
|
{ return p.negate(); }
|
|
|
|
template <typename CondT>
|
|
inline condition_parser<CondT, true>
|
|
operator~(condition_parser<CondT, false> const& p)
|
|
{ return p.negate(); }
|
|
#else // BOOST_WORKAROUND(BOOST_MSVC, == 1310) || == 1400
|
|
template <typename CondT, bool positive>
|
|
inline condition_parser<CondT, !positive>
|
|
operator~(condition_parser<CondT, positive> const& p)
|
|
{ return p.negate(); }
|
|
#endif // BOOST_WORKAROUND(BOOST_MSVC, == 1310) || == 1400
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
//
|
|
// empty_match_parser class
|
|
//
|
|
// handles expressions of the form
|
|
// epsilon_p(subject)
|
|
// where subject is a parser. The expresion returns a composite
|
|
// parser that returns an empty match if the subject parser matches.
|
|
//
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
struct empty_match_parser_gen;
|
|
struct negated_empty_match_parser_gen;
|
|
|
|
template <typename SubjectT>
|
|
struct negated_empty_match_parser; // Forward declaration
|
|
|
|
template<typename SubjectT>
|
|
struct empty_match_parser
|
|
: unary<SubjectT, parser<empty_match_parser<SubjectT> > >
|
|
{
|
|
typedef empty_match_parser<SubjectT> self_t;
|
|
typedef unary<SubjectT, parser<self_t> > base_t;
|
|
typedef unary_parser_category parser_category_t;
|
|
typedef empty_match_parser_gen parser_genererator_t;
|
|
typedef self_t embed_t;
|
|
|
|
explicit empty_match_parser(SubjectT const& p) : base_t(p) {}
|
|
|
|
template <typename ScannerT>
|
|
struct result
|
|
{ typedef typename match_result<ScannerT, nil_t>::type type; };
|
|
|
|
template <typename ScannerT>
|
|
typename parser_result<self_t, ScannerT>::type
|
|
parse(ScannerT const& scan) const
|
|
{
|
|
typename ScannerT::iterator_t save(scan.first);
|
|
|
|
typedef typename no_actions_scanner<ScannerT>::policies_t
|
|
policies_t;
|
|
|
|
bool matches = this->subject().parse(
|
|
scan.change_policies(policies_t(scan)));
|
|
if (matches)
|
|
{
|
|
scan.first = save; // reset the position
|
|
return scan.empty_match();
|
|
}
|
|
else
|
|
{
|
|
return scan.no_match();
|
|
}
|
|
}
|
|
|
|
negated_empty_match_parser<SubjectT>
|
|
negate() const
|
|
{ return negated_empty_match_parser<SubjectT>(this->subject()); }
|
|
};
|
|
|
|
template<typename SubjectT>
|
|
struct negated_empty_match_parser
|
|
: public unary<SubjectT, parser<negated_empty_match_parser<SubjectT> > >
|
|
{
|
|
typedef negated_empty_match_parser<SubjectT> self_t;
|
|
typedef unary<SubjectT, parser<self_t> > base_t;
|
|
typedef unary_parser_category parser_category_t;
|
|
typedef negated_empty_match_parser_gen parser_genererator_t;
|
|
|
|
explicit negated_empty_match_parser(SubjectT const& p) : base_t(p) {}
|
|
|
|
template <typename ScannerT>
|
|
struct result
|
|
{ typedef typename match_result<ScannerT, nil_t>::type type; };
|
|
|
|
template <typename ScannerT>
|
|
typename parser_result<self_t, ScannerT>::type
|
|
parse(ScannerT const& scan) const
|
|
{
|
|
typename ScannerT::iterator_t save(scan.first);
|
|
|
|
typedef typename no_actions_scanner<ScannerT>::policies_t
|
|
policies_t;
|
|
|
|
bool matches = this->subject().parse(
|
|
scan.change_policies(policies_t(scan)));
|
|
if (!matches)
|
|
{
|
|
scan.first = save; // reset the position
|
|
return scan.empty_match();
|
|
}
|
|
else
|
|
{
|
|
return scan.no_match();
|
|
}
|
|
}
|
|
|
|
empty_match_parser<SubjectT>
|
|
negate() const
|
|
{ return empty_match_parser<SubjectT>(this->subject()); }
|
|
};
|
|
|
|
struct empty_match_parser_gen
|
|
{
|
|
template <typename SubjectT>
|
|
struct result
|
|
{ typedef empty_match_parser<SubjectT> type; };
|
|
|
|
template <typename SubjectT>
|
|
static empty_match_parser<SubjectT>
|
|
generate(parser<SubjectT> const& subject)
|
|
{ return empty_match_parser<SubjectT>(subject.derived()); }
|
|
};
|
|
|
|
struct negated_empty_match_parser_gen
|
|
{
|
|
template <typename SubjectT>
|
|
struct result
|
|
{ typedef negated_empty_match_parser<SubjectT> type; };
|
|
|
|
template <typename SubjectT>
|
|
static negated_empty_match_parser<SubjectT>
|
|
generate(parser<SubjectT> const& subject)
|
|
{ return negated_empty_match_parser<SubjectT>(subject.derived()); }
|
|
};
|
|
|
|
//////////////////////////////
|
|
template <typename SubjectT>
|
|
inline negated_empty_match_parser<SubjectT>
|
|
operator~(empty_match_parser<SubjectT> const& p)
|
|
{ return p.negate(); }
|
|
|
|
template <typename SubjectT>
|
|
inline empty_match_parser<SubjectT>
|
|
operator~(negated_empty_match_parser<SubjectT> const& p)
|
|
{ return p.negate(); }
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
//
|
|
// epsilon_ parser and parser generator class
|
|
//
|
|
// Operates as primitive parser that always matches an empty sequence.
|
|
//
|
|
// Also operates as a parser generator. According to the type of the
|
|
// argument an instance of empty_match_parser<> (when the argument is
|
|
// a parser) or condition_parser<> (when the argument is not a parser)
|
|
// is returned by operator().
|
|
//
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
namespace impl
|
|
{
|
|
template <typename SubjectT>
|
|
struct epsilon_selector
|
|
{
|
|
typedef typename as_parser<SubjectT>::type subject_t;
|
|
typedef typename
|
|
mpl::if_<
|
|
is_parser<subject_t>
|
|
,empty_match_parser<subject_t>
|
|
,condition_parser<subject_t>
|
|
>::type type;
|
|
};
|
|
}
|
|
|
|
struct epsilon_parser : public parser<epsilon_parser>
|
|
{
|
|
typedef epsilon_parser self_t;
|
|
|
|
epsilon_parser() {}
|
|
|
|
template <typename ScannerT>
|
|
typename parser_result<self_t, ScannerT>::type
|
|
parse(ScannerT const& scan) const
|
|
{ return scan.empty_match(); }
|
|
|
|
template <typename SubjectT>
|
|
typename impl::epsilon_selector<SubjectT>::type
|
|
operator()(SubjectT const& subject) const
|
|
{
|
|
typedef typename impl::epsilon_selector<SubjectT>::type result_t;
|
|
return result_t(subject);
|
|
}
|
|
};
|
|
|
|
epsilon_parser const epsilon_p = epsilon_parser();
|
|
epsilon_parser const eps_p = epsilon_parser();
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
BOOST_SPIRIT_CLASSIC_NAMESPACE_END
|
|
|
|
}} // namespace BOOST_SPIRIT_CLASSIC_NS
|
|
|
|
#endif
|