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include/boost/spirit/utility/loops.hpp  view on Meta::CPAN

    //      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;