Implementing a "calcuator" feature

Ruby
1

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?

Soroe.

2

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

a black list.

  1. 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?