See http://www.ccs.neu.edu/home/matthias/HtDP2e/htdp2e-part1.html#(part._.D.K._design-world) and for something like 'check-with' see http://docs.racket-lang.org/teachpack/2htdpuniverse.html#(form._((lib._2htdp/universe..rkt)._check-with))
On Oct 5, 2010, at 7:30 AM, 김태윤 wrote: > hello > I am a scheme beginner > I am learning big-bang function with the book, how to design programs > but I still have no idea how big-bang function exactly work. > > #lang racket > (require 2htdp/image) > (require 2htdp/universe) > (define (handle-draw model) (text model 18 "blue")) > (define (handle-key old-model key) key) > (big-bang "" ; initial model is empty string > (check-with string?) ; model is a string > (on-draw handle-draw 400 50) ; display text in 150x50 pixel window > (on-key handle-key)) > > could somebody please tell me how this code exactly work? > my guessing is this > > there is only one checking function. > if it is true, keep big-bang going. > if it is false, it stops. > the first argument of big-bang "" is going to be sent to handle-draw by > on-draw > if key pressed, that handle-draw's return value is going to be sent to > handle-key as second argument by on-key > big-bang's first argument "" is changed to the handle-key's return value. > and big-bang start again from the beginning with that value as first argument > > I still have no idea about the old-model argument. > is check-with function must be there? > > thanks in advanced > > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/users _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
