Sorry, but I meant that it has to compute the final result. What would you recommend to do that ?
Why don't you look for yourself here: $BOOST_ROOT/libs/spirit/example/qi/calc3.cpp (or any of the more complex calculator examples)? Regards Hartmut --------------- http://boost-spirit.com
2010/11/30 Eloi Du Bois <eloi.du.bois@gmail.com> Wow ! Excellent :)
I thought it would be more verbose than that.
Thank you very much, Eloi Du Bois. 2010/11/30 Hartmut Kaiser <hartmut.kaiser@gmail.com>
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.
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<Iterator, qi::space_type> { calculator() : calculator::base_type(expression) { expression = term >> *( ('+' >> term) | ('-' >> term) ) ; term = factor >> *( ('*' >> factor) | ('/' >> factor) ) ; factor = qi::uint_ | '(' >> expression >> ')' | ('-' >> factor) | ('+' >> factor) ; } qi::rule<Iterator, qi::space_type> expression, term, factor; };
And here is how to use it:
std::string input("1+2/3"); calculator<std::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
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