[racket] Couldn't find a step matching that criterion

From: David Van Horn (dvanhorn at ccs.neu.edu)
Date: Sun Jan 9 20:48:49 EST 2011

On 1/9/11 9:02 AM, Sayth Renshaw wrote:
> I am having a real issue with the stepper. Maybe the programs are too
> simple so far for the stepper, but it doesn't step.
> The check syntax feature is great. for the check-color game should the
> stepper work? What is the trick? I just wanted to check the flow by
> stepping through.
> Each time I use it I get "Couldn't find a step matching that criterion"
> No matter what I change select or do.
> ;check-color
> ;colour guessing game (target target)(guess guess)
> ;symbol symbol symbol symbol -> string
> ;four color symbols
> (define (check-color target1 target2 guess1 guess2)
>    (cond
>      [(eq? target1 guess1) 'Perfect]
>      [(or (eq? target1 guess1)(eq? target2 guess2))
> 'OneColorAtCorrectPosition]
>      [(or (eq? target1 guess2)(eq? target2 guess1)) 'OneColorOccurs]
>      [else 'NothingCorrect]))
> ;(check-color 'red 'green 'green 'red)
> ;'OneColorOccurs


You need to have at least one expression to step through in order for 
the stepper to work.  The program you've given consists of a single 
definition and *no* expressions.

The fix is easy: uncomment the check-color expression you have and step 
through its computation.


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