From MHCGraphics
; Mead example file -- a countdown
;
; Jim Teresco
; Computer Science 110
; Mount Holyoke College
;
; Borrowed from Duane A. Bailey, Williams College
;
; This is really just Scheme example - it doesn't make use
; of Mead
;
; $Id: Countdown.scm 569 2008-03-24 02:09:18Z terescoj $
;
; Here's a function that counts 10 ... 2 1 blastoff!
; It's self referential, or recursive.
(define (countdown n)
; if takes 3 parameters: the first is a condition, the
; second and third are functions (or s-expressions).
; if the condition is true, the function in the second
; parameter is executed, otherwise the function in the
; third parameter is executed
(if (<= n 0)
(print "Blastoff!") ; simple case
(begin ; this begin wraps 3 s-exprs into 1
(print n) ; prints the value of n (as you might guess)
(newline) ; advance the output to the next line
; at this point, we've printed the value of n. In
; order to complete our countdown, we need to count
; (n-1), (n-2), ..., 1. Well, we have a function that
; can do that (which we just happen to be writing
; right now), but we just go ahead and call it.
(countdown (- n 1)) ; recursion happens here
)
)
)
