On Apr 2, 2012, at 7:29 AM, Roelof Wobben wrote:
> I like the way you do these things.
> but what did you mean with "p-x" ?
p-x doesn't exist, but it's a mistake my students often make:
(define p (make-posn 3 5))
...
p-x ; they expect 3, but get an error message instead.
> Following your way o
Op 2-4-2012 13:02, Stephen Bloch schreef:
On Apr 2, 2012, at 3:25 AM, Pierpaolo Bernardi quoted:
I thought that the position of the ufo can be find at (posn-y p) and
(posn-x) because the postition is a struct of Posn.
and replied:
You must pay more attention to small details. What is the p i
On Apr 2, 2012, at 3:25 AM, Pierpaolo Bernardi quoted:
>> I thought that the position of the ufo can be find at (posn-y p) and
>> (posn-x) because the postition is a struct of Posn.
and replied:
> You must pay more attention to small details. What is the p in (posn-y
> p)? Isn't an argument mi
On Fri, Mar 30, 2012 at 16:56, Roelof Wobben wrote:
> Op 30-3-2012 12:17, Pierpaolo Bernardi schreef:
>
>> On Fri, Mar 30, 2012 at 11:53, Roelof Wobben wrote:
>>>
>>> Op 30-3-2012 9:46, Pierpaolo Bernardi schreef:
>>>
Hello Roelof,
On Fri, Mar 30, 2012 at 09:32, Roelof Wobben wr
Op 30-3-2012 12:17, Pierpaolo Bernardi schreef:
On Fri, Mar 30, 2012 at 11:53, Roelof Wobben wrote:
Op 30-3-2012 9:46, Pierpaolo Bernardi schreef:
Hello Roelof,
On Fri, Mar 30, 2012 at 09:32, Roelof Wobbenwrote:
(define (show-ufo ufo)
(place-image BLU (ufo-loc u) MTS))
But still I c
Op 30-3-2012 9:46, Pierpaolo Bernardi schreef:
Hello Roelof,
On Fri, Mar 30, 2012 at 09:32, Roelof Wobben wrote:
(define (show-ufo ufo)
(place-image BLU (ufo-loc u) MTS))
But still I can't get the show-ufo work.
Check carefully the name of your variables!
Doesn't DrRacket give you an exp
Hello Roelof,
On Fri, Mar 30, 2012 at 09:32, Roelof Wobben wrote:
> (define (show-ufo ufo)
> (place-image BLU (ufo-loc u) MTS))
>
> But still I can't get the show-ufo work.
Check carefully the name of your variables!
Doesn't DrRacket give you an explicative error message in this case?
P.
__
Sorry, I forget to give you the chapter and the book.
Im talking about this chapter
2.5.2Programming with Structures Which can be found at this
url:
http://www.ccs.neu.edu/home/matthias/HtDP2e/htdp2e-part1.html#%28part._structure%29
Roelof
Op 30-3-2012 9:32, Roelof
Hello,
I try to make the ufo exercise work on this chapter :
So I have this :
; visual constants
(define MTS (empty-scene 100 100))
(define BLU (place-image (rectangle 25 25 "solid" "blue") 50 50 MTS))
(define-struct velocity (dx dy))
; A Velocity is a structure: (make-vel Number Number)
; int
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