[racket] display problem

From: Roelof Wobben (r.wobben at home.nl)
Date: Wed Apr 11 12:03:23 EDT 2012

Op 11-4-2012 15:10, Stephen Bloch schreef:
> On Apr 11, 2012, at 7:39 AM, Roelof Wobben<r.wobben at home.nl>  wrote:
>> But I see something strange, Both check-expect of the function width gives as output 18.
>> But I expect that on a empty (editor-pre verwerker) gives as output 0.
>> Am I mistaken or is there something wrong in my functions ?
> Yes, there's something wrong with your width function.  It's nothing subtle or complicated; you can figure it out just by looking at the two-line definition of that function.
> In addition, the contract of the function is wrong: you say it takes in an image, but your test cases give it an editor instead.
> More broadly, you're doing the whole problem the hard way.  Why do you need to know the width of anything?  I would do this whole problem without an image-width, without arithmetic, without a place-image, using the functions in the 2htdp/image library.
> Stephen Bloch
> sbloch at adelphi.edu


I changed the contract to Editor -> Number.
When I change the make-editor function the value changed.
So I think the check-expect is wrong but I have no clue how to change it.

I find the way with overlay and beside more the hard way. I have puzzled 
a lot of time with it without success and this solution cost me a half a 


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