Re: evaluating an expression while parsing

On Sun, 11 Jul 2004, [email protected] wrote:

> The question here is that I'd like to be able to evaluate the above
> statements by passing in some values for num_oranges, num_apples,
> has_override, etc. Idealy, I'd like to be able to give it a hashref
> with all of these variables and then have PRD spit out true or false
> for the final result. I was thinking about using the $arg facility and
> calling it as such:
>     my $result = $parser->start($expression, 1, $parameters);
> but passing $arg around seems to be a fairly messy way to do this.  In
> fact, do I even want to be attempting to evaluate this from within
> PRD, or should I be building a parsetree and doing it separately?
> Some guidance would be appreciated.  Thanks.

You can do this at parse time, but it's better to build a symbolic
parse tree and evaluate it later IMHO.  See my cfperl package
http://lifelogs.com/cfperl for a sample implementation.

(I think this was recently discussed on this list, too)

Ted