Re: [Boost-users] Parsing math expression

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Is there a simple math expression parser in boost ? I only need to parse those kind of expression: "1+2/3". I believe Spirit is exactly what you're looking for. It has almost a dozen different calculator examples to choose from as a starting point for your needs.

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I have been thinking on boost::spirit, but it is quite hard for what I need. Why?

I very enjoy playing with spirit, but I was looking for a 5-line code that only boost have the secret...

Well, not exactly five lines, but here is a simple calculator grammar written in Spirit: namespace qi = boost::spirit::qi; template <typename Iterator> struct calculator : qi::grammar { calculator() : calculator::base_type(expression) { expression = term >> *( ('+' >> term) | ('-' >> term) ) ; term = factor >> *( ('*' >> factor) | ('/' >> factor) ) ; factor = qi::uint_ | '(' >> expression >> ')' | ('-' >> factor) | ('+' >> factor) ; } qi::rule expression, term, factor; }; And here is how to use it: std::string input("1+2/3"); calculatorstd::string::const_iterator calc; if (phrase_parse(input.begin(), input.end(), calc, qi::space)) std::cout << "successfully parsed: " << input << std::endl; Regards Hartmut --------------- http://boost-spirit.com