Function digits

include/boost/parser/parser.hpp:6045–6057

            integral numeric parsers like `int_` and `uint_`. */
        template<int Digits>
        constexpr auto digits() const noexcept
        {
            if constexpr (detail::has_digits1_member_function_template_v<
                              parser_type>) {
                return parser::parser_interface{
                    parser_.template digits<Digits>()};
            } else {
                static_assert(
                    detail::has_digits1_member_function_template_v<parser_type>,
                    "Only certain parsers have a .base<>() member function. "
                    "This is not one of them.");
            }
        }

        /** Returns a new `parser_interface` constructed from
            `parser_.digits<MinDigits2, MaxDigits2>()`.  Note that this only