loops.hpp

来自「CGAL is a collaborative effort of severa」· HPP 代码 · 共 314 行

/*=============================================================================
    Copyright (c) 1998-2003 Joel de Guzman
    Copyright (c) 2002 Raghavendra Satish
    Copyright (c) 2002 Jeff Westfahl
    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_LOOPS_HPP)
#define BOOST_SPIRIT_LOOPS_HPP

///////////////////////////////////////////////////////////////////////////////
#include <boost/spirit/core/parser.hpp>
#include <boost/spirit/core/composite/composite.hpp>

///////////////////////////////////////////////////////////////////////////////
namespace boost { namespace spirit {

    ///////////////////////////////////////////////////////////////////////////
    //
    //  fixed_loop class
    //
    //      This class takes care of the construct:
    //
    //          repeat_p (exact) [p]
    //
    //      where 'p' is a parser and 'exact' is the number of times to
    //      repeat. The parser iterates over the input exactly 'exact' times.
    //      The parse function fails if the parser does not match the input
    //      exactly 'exact' times.
    //
    //      This class is parametizable and can accept constant arguments
    //      (e.g. repeat_p (5) [p]) as well as references to variables (e.g.
    //      repeat_p (ref (n)) [p]).
    //
    ///////////////////////////////////////////////////////////////////////////
    template <typename ParserT, typename ExactT>
    class fixed_loop
    : public unary<ParserT, parser <fixed_loop <ParserT, ExactT> > >
    {
    public:

        typedef fixed_loop<ParserT, ExactT>     self_t;
        typedef unary<ParserT, parser<self_t> >  base_t;

        fixed_loop (ParserT const & subject, ExactT const & exact)
        : base_t(subject), m_exact(exact) {}

        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;
            result_t hit = scan.empty_match();
            std::size_t n = m_exact;

            for (std::size_t i = 0; i < n; ++i)
            {
                if (result_t next = this->subject().parse(scan))
                {
                    scan.concat_match(hit, next);
                }
                else
                {
                    return scan.no_match();
                }
            }

            return hit;
        }

        template <typename ScannerT>
        struct result
        {
            typedef typename match_result<ScannerT, nil_t>::type type;
        };

    private:

        ExactT m_exact;
    };

    ///////////////////////////////////////////////////////////////////////////////
    //
    //  finite_loop class
    //
    //      This class takes care of the construct:
    //
    //          repeat_p (min, max) [p]
    //
    //      where 'p' is a parser, 'min' and 'max' specifies the minimum and
    //      maximum iterations over 'p'. The parser iterates over the input
    //      at least 'min' times and at most 'max' times. The parse function
    //      fails if the parser does not match the input at least 'min' times
    //      and at most 'max' times.
    //
    //      This class is parametizable and can accept constant arguments
    //      (e.g. repeat_p (5, 10) [p]) as well as references to variables
    //      (e.g. repeat_p (ref (n1), ref (n2)) [p]).
    //
    ///////////////////////////////////////////////////////////////////////////////
    template <typename ParserT, typename MinT, typename MaxT>
    class finite_loop
    : public unary<ParserT, parser<finite_loop<ParserT, MinT, MaxT> > >
    {
    public:

        typedef finite_loop <ParserT, MinT, MaxT> self_t;
        typedef unary<ParserT, parser<self_t> >   base_t;

        finite_loop (ParserT const & subject, MinT const & min, MaxT const & max)
        : base_t(subject), m_min(min), m_max(max) {}

        template <typename ScannerT>
        typename parser_result <self_t, ScannerT>::type
        parse(ScannerT const & scan) const
        {
            BOOST_SPIRIT_ASSERT(m_min <= m_max);
            typedef typename parser_result<self_t, ScannerT>::type result_t;
            result_t hit = scan.empty_match();

            std::size_t n1 = m_min;
            std::size_t n2 = m_max;

            for (std::size_t i = 0; i < n2; ++i)
            {
                typename ScannerT::iterator_t save = scan.first;
                result_t next = this->subject().parse(scan);
 
                if (!next)
                {
                    if (i >= n1)
                    {
                        scan.first = save;
                        break;
                    }
                    else
                    {
                        return scan.no_match();
                    }
                }

                scan.concat_match(hit, next);
            }

            return hit;
        }

        template <typename ScannerT>
        struct result
        {
            typedef typename match_result<ScannerT, nil_t>::type type;
        };

    private:

        MinT    m_min;
        MaxT    m_max;
    };

    ///////////////////////////////////////////////////////////////////////////////
    //
    //  infinite_loop class
    //
    //      This class takes care of the construct:
    //
    //          repeat_p (min, more) [p]
    //
    //      where 'p' is a parser, 'min' is the minimum iteration over 'p'
    //      and more specifies that the iteration should proceed
    //      indefinitely. The parser iterates over the input at least 'min'
    //      times and continues indefinitely until 'p' fails or all of the
    //      input is parsed. The parse function fails if the parser does not
    //      match the input at least 'min' times.
    //
    //      This class is parametizable and can accept constant arguments
    //      (e.g. repeat_p (5, more) [p]) as well as references to variables
    //      (e.g. repeat_p (ref (n), more) [p]).
    //
    ///////////////////////////////////////////////////////////////////////////////

    struct more_t {};
    more_t const more = more_t ();

    template <typename ParserT, typename MinT>
    class infinite_loop
     : public unary<ParserT, parser<infinite_loop<ParserT, MinT> > >
    {
    public:

        typedef infinite_loop <ParserT, MinT>   self_t;
        typedef unary<ParserT, parser<self_t> > base_t;

        infinite_loop (
            ParserT const& subject,
            MinT const& min,
            more_t const&
        )
        : base_t(subject), m_min(min) {}

        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;
            result_t hit = scan.empty_match();
            std::size_t n = m_min;

            for (std::size_t i = 0; ; ++i)
            {
                typename ScannerT::iterator_t save = scan.first;
                result_t next = this->subject().parse(scan);

                if (!next)
                {
                    if (i >= n)
                    {
                        scan.first = save;
                        break;
                    }
                    else
                    {
                        return scan.no_match();
                    }
                }

                scan.concat_match(hit, next);
            }

            return hit;
        }

        template <typename ScannerT>
        struct result
        {
            typedef typename match_result<ScannerT, nil_t>::type type;
        };

        private:

        MinT m_min;
    };

    template <typename ExactT>
    struct fixed_loop_gen
    {
        fixed_loop_gen (ExactT const & exact)
        : m_exact (exact) {}

        template <typename ParserT>
        fixed_loop <ParserT, ExactT>
        operator[](parser <ParserT> const & subject) const
        {
            return fixed_loop <ParserT, ExactT> (subject.derived (), m_exact);
        }

        ExactT m_exact;
    };

    namespace impl {

        template <typename ParserT, typename MinT, typename MaxT>
        struct loop_traits
        {
            typedef typename mpl::if_<
                boost::is_same<MaxT, more_t>,
                infinite_loop<ParserT, MinT>,
                finite_loop<ParserT, MinT, MaxT>
            >::type type;
        };

    } // namespace impl

    template <typename MinT, typename MaxT>
    struct nonfixed_loop_gen
    {
       nonfixed_loop_gen (MinT min, MaxT max)
        : m_min (min), m_max (max) {}

       template <typename ParserT>
       typename impl::loop_traits<ParserT, MinT, MaxT>::type
       operator[](parser <ParserT> const & subject) const
       {
           typedef typename impl::loop_traits<ParserT, MinT, MaxT>::type ret_t;
           return ret_t(
                subject.derived(),
                m_min,
                m_max);
       }

       MinT m_min;
       MaxT m_max;
    };

    template <typename ExactT>
    fixed_loop_gen <ExactT>
    repeat_p(ExactT const & exact)
    {
        return fixed_loop_gen <ExactT> (exact);
    }

    template <typename MinT, typename MaxT>
    nonfixed_loop_gen <MinT, MaxT>
    repeat_p(MinT const & min, MaxT const & max)
    {
        return nonfixed_loop_gen <MinT, MaxT> (min, max);
    }

}} // namespace boost::spirit

#endif // #if !defined(BOOST_SPIRIT_LOOPS_HPP)