On Apr 11, 2012, at 7:39 AM, Roelof Wobben <r.wob...@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
sbl...@adelphi.edu
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