From: George Ogata <g_ogata@...>
Date: 2005-04-29T20:13:05+09:00
Subject: Re: I need a formula parser

Joel VanderWerf <vjoel@PATH.Berkeley.EDU> writes:

> Daniel Berger wrote:
>> However, I still do not have a formula parser.  John's module uses
>> Parse::RecDescent to parse formulas.  I need something similar (or
>> better).  Preferably something generic that everyone can use and enjoy,
>> but I'll take a more tailored parser if necessary.
>
> Might help...
>
> http://www.ruby-talk.org/cgi-bin/scat.rb/ruby/ruby-talk/110483

I have a more complete C parser at cast.rubyforge.org, if it's not too
overkill for you.  Here's a demo:

irb(main):001:0> require 'cast/cast'
=> true
irb(main):002:0> C::Expression.parse('sin(x / 180.0 * M_PI)')
=> Call
    expr: Variable
        name: "sin"
    args: 
        - Multiply
            expr1: Divide
                expr1: Variable
                    name: "x"
                expr2: FloatLiteral
                    val: 180.0
            expr2: Variable
                name: "M_PI"