Hello everyone Is it expected behavior, that code like this: typedef uint_parser<double> uint_double_parser; my_rule_t max_59_uint = max_limit_d<double>(59.) [ uint_double_parser() ] [max_59_uint.value = arg1] ; causes assertion on input like "" or "aaa"? Investigating problem, I found that in function parse(ScannerT const& scan) const hit.value() used directly, without checking if it valid (see original code). If it is expected use, then what function parser_result::has_valid_attribute() for ? I've modified function parse(ScannerT const& scan) const (see my code) and everything works fine, but I'm not sure if such modification is "legitimate" and does not break anything else. original code (<boost_1_31_0>\boost\spirit\core\composite\directives.hpp): /////////////////////////////////////////////////////////////////////////// // // max_bounded class // /////////////////////////////////////////////////////////////////////////// template <typename BoundsT> struct max_bounded_gen; template <typename ParserT, typename BoundsT> struct max_bounded : public unary<ParserT, parser<max_bounded<ParserT, BoundsT> > > { typedef max_bounded<ParserT, BoundsT> self_t; typedef unary_parser_category parser_category_t; typedef max_bounded_gen<BoundsT> parser_generator_t; typedef unary<ParserT, parser<self_t> > base_t; template <typename ScannerT> struct result { typedef typename parser_result<ParserT, ScannerT>::type type; }; max_bounded(ParserT const& p, BoundsT const& max__) : base_t(p) , max_(max__) {} 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 = this->subject().parse(scan); if (hit.value() > max_) // ^^^^^^^^^^^ no check for validity return scan.no_match(); return hit; } BoundsT max_; }; my code: /////////////////////////////////////////////////////////////////////////// // // max_bounded class // /////////////////////////////////////////////////////////////////////////// template <typename BoundsT> struct max_bounded_gen; template <typename ParserT, typename BoundsT> struct max_bounded : public unary<ParserT, parser<max_bounded<ParserT, BoundsT> > > { typedef max_bounded<ParserT, BoundsT> self_t; typedef unary_parser_category parser_category_t; typedef max_bounded_gen<BoundsT> parser_generator_t; typedef unary<ParserT, parser<self_t> > base_t; template <typename ScannerT> struct result { typedef typename parser_result<ParserT, ScannerT>::type type; }; max_bounded(ParserT const& p, BoundsT const& max__) : base_t(p) , max_(max__) {} 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 = this->subject().parse(scan); if (!hit.has_valid_attribute() || hit.value() > max_) // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ is this right ? return scan.no_match(); return hit; } BoundsT max_; }; -- Best regards, Vladimir mailto:vkrasovsky@yandex.ru