Re: [Boost-users] Parsing math expression

Subject: Re: [Boost-users] Parsing math expression
From: Eloi Du Bois (eloi.du.bois_at_[hidden])
Date: 2010-11-30 09:47:01

Ok, thank you for the link.

2010/11/30 Hartmut Kaiser <hartmut.kaiser_at_[hidden]>

> > 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_at_[hidden]> 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_at_[hidden]>
> > > > > 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
> >
> >
> >
> > _______________________________________________
> > Boost-users mailing list
> > Boost-users_at_[hidden]
> > http://lists.boost.org/mailman/listinfo.cgi/boost-users
> >
>
>
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