On Fri, Jul 15, 2011 at 11:56 AM, Stephen Bloch <sbl...@adelphi.edu> wrote: > Last Monday I attended Dan Garcia's workshop on BYOB. He kept pointing out > (presumably for the benefit of Emmanuel and me) that it really is a > functional language. And yes, it has "map", "filter", "foldl", and > "lambda"... but most of the examples and assignments one normally does in > BYOB use very stateful turtle graphics. So naturally I thought "Could I > simulate this in universe?" > > I defined a sprite struct (with an icon, a location, a direction, a pen, > etc.) and a world struct (with a list of sprites and a picture), and wrote a > bunch of low-level operations on these that would obviously be needed. So > far so good. I'm imagining that student code might say something like > > ; zigzag : sprite -> sprite > (define (zigzag sprite) > (move 10 (rotate-cw 45 (move 10 (rotate-ccw sprite))))) > ... > (define this-sprite (make-sprite (bitmap "sprite-icon.png") (make-posn > 0 0) 0 ... zigzag) > ... > (run-byob-world (list this-sprite that-sprite third-sprite) > initial-background-picture) > which would in turn call big-bang with a prewritten draw handler and a tick > handler that calls each sprite's action on it.
I see you're already representing the World as a picture and a list of sprites, so just let the kids manipulate that directly. Since you want to support multiple sprites, what if each sprite in the sprite list had a name, so the contract is: move: String (sprite-name) Integer (distance) World -> World So: (define (zigzag sprite-name world) (move sprite-name 10 (rotate-cw sprite-name 45 (move sprite-name 10 (rotate-ccw sprite-name world))))) You could also provide functions to add and delete sprites from the world. add-sprite: String (sprite-name) Posn (start-location) World -> World delete-sprite: String (sprite-name) World -> World Then, give them some sort of blank-canvas which is a make-world that has an empty list of sprites and an empty scene as the picture. _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
