On Jul 16, 2011, at 10:34 AM, Matthias Felleisen wrote:
> Since these people have no scruples -- don't even understand that they dont
> have any -- go for the imperative version.
I have a hard time believing that EVERY CS educator who evangelizes for
something other than PBD "has no scruples". And for people like Dan Garcia who
are not only gifted teachers but knowledgeable about functional programming,
I'd rather try to persuade and find areas of mutual agreement.
>> Every workshop on Python or Processing in education includes an example
>> ("which students can do on the first day," although largely by copying and
>> tinkering rather than deep understanding)
>
> We can do an animation on the first day. Our students actually understand
> what they do and why it works. And the idea is 100% algebra. So why cave? Why
> not attack them?
Oh, map-image and build-image are clean and functional (at least from the
student's perspective); I don't see them as "caving" at all.
I went to a talk at SIGCSE in which somebody posted one of these Python or
Processing examples, so I opened DrRacket on my laptop, spent a minute
re-coding it using build-image, then showed it to her (applied to her own face
off her Web site) after the talk:
(define (diag-mirror pic)
(build-image (image-width pic) (image-width pic)
(lambda (x y)
(if (> x y)
(get-pixel-color x y pic)
(get-pixel-color y x pic)))))
Likewise, there's the Stone "random art" assignment from nifty.stanford.edu:
it's easy to do in Python or Processing with nested for-loops, but it's even
easier to do with build-image. I think pretty much any example of this sort
that you find in a Python or Processing book can be done with map-image,
build-image, and function closures.
Replicating the BYOB exercises is more difficult, and I'm sure there will be
heavily-imperative things that I can't translate into any kind of natural
functional code, but I'd like to be able to translate a lot of the standard
beginning exercises.
(Hmm... simulate "wait" by replacing the "action" of the current sprite with a
function that checks the clock time and then invokes the current
continuation....)
Stephen Bloch
sbl...@adelphi.edu
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