[racket] display problem

From: Roelof Wobben (r.wobben at home.nl)
Date: Thu Apr 12 02:38:46 EDT 2012

Op 11-4-2012 18:03, Roelof Wobben schreef:
> 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
> Oke,
> 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 hour.
> Roelof

Nobody who can give me a tip what's wrong with the function.


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