numerics.ipp

boost库提供标准的C++ API 配合dev c++使用,功能更加强大

                int Radix,
                unsigned MinDigits,
                int MaxDigits,
                typename Accumulate
            >
            struct apply
            {
                typedef extract_int_base<Radix, Accumulate> base;
                typedef radix_traits<Radix> check;

                template <typename ScannerT, typename T>
                static bool
                f(ScannerT& scan, T& n, std::size_t& count)
                {
                    std::size_t i = 0;
                    for (; !scan.at_end() && check::is_valid(*scan);
                        ++i, ++scan, ++count)
                    {
                        if (!base::f(scan, n))
                            return false;   //  over/underflow!
                    }
                    return i >= MinDigits;
                }
            };
        };

        //////////////////////////////////
        template <
            int Radix, unsigned MinDigits, int MaxDigits,
            typename Accumulate = positive_accumulate<Radix>
        >
        struct extract_int
        {
            template <typename ScannerT, typename T>
            static bool
            f(ScannerT& scan, T& n, std::size_t& count)
            {
                return extract_int_<(MaxDigits >= 0)>::template
                    apply<Radix, MinDigits, MaxDigits, Accumulate>::
                        f(scan, n, count);
            }
        };

        ///////////////////////////////////////////////////////////////////////
        //
        //  uint_parser_impl class
        //
        ///////////////////////////////////////////////////////////////////////
        template <
            typename T = unsigned,
            int Radix = 10,
            unsigned MinDigits = 1,
            int MaxDigits = -1
        >
        struct uint_parser_impl
            : parser<uint_parser_impl<T, Radix, MinDigits, MaxDigits> >
        {
            typedef uint_parser_impl<T, Radix, MinDigits, MaxDigits> self_t;

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

            template <typename ScannerT>
            typename parser_result<self_t, ScannerT>::type
            parse(ScannerT const& scan) const
            {
                if (!scan.at_end())
                {
                    T n = 0;
                    std::size_t count = 0;
                    typename ScannerT::iterator_t save = scan.first;
                    if (extract_int<Radix, MinDigits, MaxDigits>::
                        f(scan, n, count))
                    {
                        return scan.create_match(count, n, save, scan.first);
                    }
                    // return no-match if number overflows
                }
                return scan.no_match();
            }
        };

        ///////////////////////////////////////////////////////////////////////
        //
        //  int_parser_impl class
        //
        ///////////////////////////////////////////////////////////////////////
        template <
            typename T = unsigned,
            int Radix = 10,
            unsigned MinDigits = 1,
            int MaxDigits = -1
        >
        struct int_parser_impl
            : parser<int_parser_impl<T, Radix, MinDigits, MaxDigits> >
        {
            typedef int_parser_impl<T, Radix, MinDigits, MaxDigits> self_t;

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

            template <typename ScannerT>
            typename parser_result<self_t, ScannerT>::type
            parse(ScannerT const& scan) const
            {
                typedef extract_int<Radix, MinDigits, MaxDigits,
                    negative_accumulate<Radix> > extract_int_neg_t;
                typedef extract_int<Radix, MinDigits, MaxDigits>
                    extract_int_pos_t;

                if (!scan.at_end())
                {
                    T n = 0;
                    std::size_t count = 0;
                    typename ScannerT::iterator_t save = scan.first;

                    bool hit = impl::extract_sign(scan, count);

                    if (hit)
                        hit = extract_int_neg_t::f(scan, n, count);
                    else
                        hit = extract_int_pos_t::f(scan, n, count);

                    if (hit)
                        return scan.create_match(count, n, save, scan.first);
                    else
                        scan.first = save;
                    // return no-match if number overflows or underflows
                }
                return scan.no_match();
            }
        };

        ///////////////////////////////////////////////////////////////////////
        //
        //  real_parser_impl class
        //
        ///////////////////////////////////////////////////////////////////////
#if (defined(BOOST_MSVC) && (BOOST_MSVC <= 1310))
#pragma warning(push)
#pragma warning(disable:4127)
#endif

        template <typename RT, typename T, typename RealPoliciesT>
        struct real_parser_impl
        {
            typedef real_parser_impl<RT, T, RealPoliciesT> self_t;

            template <typename ScannerT>
            RT parse_main(ScannerT const& scan) const
            {
                if (scan.at_end())
                    return scan.no_match();
                typename ScannerT::iterator_t save = scan.first;

                typedef typename parser_result<sign_parser, ScannerT>::type
                    sign_match_t;
                typedef typename parser_result<chlit<>, ScannerT>::type
                    exp_match_t;

                sign_match_t    sign_match = RealPoliciesT::parse_sign(scan);
                std::size_t     count = sign_match ? sign_match.length() : 0;
                bool            neg = sign_match.has_valid_attribute() ?
                                    sign_match.value() : false;

                RT              n_match = RealPoliciesT::parse_n(scan);
                T               n = n_match.has_valid_attribute() ?
                                    n_match.value() : T(0);
                bool            got_a_number = n_match;
                exp_match_t     e_hit;

                if (!got_a_number && !RealPoliciesT::allow_leading_dot)
                     return scan.no_match();
                else
                    count += n_match.length();

                if (neg)
                    n = -n;

                if (RealPoliciesT::parse_dot(scan))
                {
                    //  We got the decimal point. Now we will try to parse
                    //  the fraction if it is there. If not, it defaults
                    //  to zero (0) only if we already got a number.

                    if (RT hit = RealPoliciesT::parse_frac_n(scan))
                    {
                        hit.value(hit.value()
                            * BOOST_SPIRIT_IMPL_STD_NS::
                                pow(T(10), T(-hit.length())));
                        if (neg)
                            n -= hit.value();
                        else
                            n += hit.value();
                        count += hit.length() + 1;

                    }

                    else if (!got_a_number ||
                        !RealPoliciesT::allow_trailing_dot)
                        return scan.no_match();

                    e_hit = RealPoliciesT::parse_exp(scan);
                }
                else
                {
                    //  We have reached a point where we
                    //  still haven't seen a number at all.
                    //  We return early with a no-match.
                    if (!got_a_number)
                        return scan.no_match();

                    //  If we must expect a dot and we didn't see
                    //  an exponent, return early with a no-match.
                    e_hit = RealPoliciesT::parse_exp(scan);
                    if (RealPoliciesT::expect_dot && !e_hit)
                        return scan.no_match();
                }

                if (e_hit)
                {
                    //  We got the exponent prefix. Now we will try to parse the
                    //  actual exponent. It is an error if it is not there.
                    if (RT e_n_hit = RealPoliciesT::parse_exp_n(scan))
                    {
                        n *= BOOST_SPIRIT_IMPL_STD_NS::
                            pow(T(10), T(e_n_hit.value()));
                        count += e_n_hit.length() + e_hit.length();
                    }
                    else
                    {
                        //  Oops, no exponent, return a no-match
                        return scan.no_match();
                    }
                }

                return scan.create_match(count, n, save, scan.first);
            }

            template <typename ScannerT>
            static RT parse(ScannerT const& scan)
            {
                static self_t this_;
                return impl::implicit_lexeme_parse<RT>(this_, scan, scan);
            }
        };

#if (defined(BOOST_MSVC) && (BOOST_MSVC <= 1310))
#pragma warning(pop)
#pragma warning(disable:4127)
#endif

    }   //  namespace impl

///////////////////////////////////////////////////////////////////////////////
}} // namespace boost::spirit

#endif
#undef BOOST_SPIRIT_IMPL_STD_NS