[racket] image equality and evaluators

From: Jordan Johnson (jmj at fellowhuman.com)
Date: Thu Feb 9 21:40:00 EST 2012

Hi all,


#lang racket

(require racket/sandbox lang/imageeq)

(define ev

  (make-evaluator '(special beginner)

                  #:requires '(2htdp/image)))


> (image? (ev '(rectangle 2 2 'solid 'blue)))


> (image=? (ev '(rectangle 2 2 'solid 'blue))
>            (ev '(rectangle 2 2 'solid 'blue)))
> image=?: expects type <image> as 1st argument, given: (object:image% ... )
> ... [etc., redacted]

But the REPL renders (ev '(rectangle 2 2 'solid 'blue))) as a picture of a
tiny rectangle, as I would expect.

How is the above exposing the difference between image=?'s perception of an
image, and the object implementing the image?

And, more importantly, is there a way to make (meaningful) image
comparisons across the boundary imposed by the sandbox?

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