From: Mat Schaffer <schapht@...>
Date: 2006-06-05T21:35:12+09:00
Subject: Re: parsing a boolean expression


On Jun 5, 2006, at 2:32 AM, Daniel Baird wrote:
> Hi all,
>
> I need to take a string typed by dirty users' fingers, that should  
> contain a
> boolean expression, like this:
>  one and (two or three or (four and five) or six) and (seven or eight)
> ..and parse it into some kind of sensible data structure, like a  
> tree or
> something.   Or reject it if it's mal-formed.
>
> I figure it might take me two or three days to write and debug from  
> scratch
> (..hey, I'm fairly new to Ruby :\ ), but I'm sure there's a library
> somewhere that will do the job.
>
> I've tried searching for bool*, expr* and pars* in fxri but didn't get
> anything, and Googling just tells me that my search terms are too  
> generic to
> find what I want. Any suggestions?
>
> Thanks in advance!
>
> ;Daniel
>
> -- 
> Daniel Baird
> http://danielbaird.com (TiddlyW;nks! :: Whiteboard Koala :: Blog ::  
> Things
> That Suck)

If you can force (or just add on) an exterior set of parenthesis, S- 
Expressions could fill your parsing need as described here:
http://www.artima.com//rubycs/articles/patterns_sexp_dsls3.html

You'll have to work out the booleans yourself, but that shouldn't be  
too tricky.

-Mat