From: Jeremy Tregunna <jtregunna@...>
Date: 2007-01-21T09:57:50+09:00
Subject: Re: Implementing a "calcuator" feature

On 20-Jan-07, at 7:42 PM, Sonny Chee wrote:

> Hey Guys,
>
> Can someone recommend a fast but robust way to implement a calculator
> feature? I want to allow my users the ability to enter simple agebraic
> expressions and then press 'calc'.
>
> My initial thought was to:
>
> 1) Check the expression for "bad words" and escapes by checking  
> against
> a black list.
>
> 2) Any expressions that pass step 1 are then evaluated with 'eval'.
>
> Anyone have better ideas?  In terms of the black list, does anyone  
> know
> how I can load the list of ruby reserved words without having to
> actually type them all in by hand?

Why not just write a parser for algebraic expressions?

--
jer