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;                          do.scm
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(define (do-demo)
  (do ((i 1 (+ i 1))) ; local, init, inc
      ((> i 10) i)    ; terminating condition and return value
    (print i))
  (do ((l '(a b c d e f g) (cdr l)))
      ((null? l) 'fini)
    (print l)))

;;;
;;; NOTE
;;; can you define while as a recursive function?
;;;                for                          ?
;;;


(define (fact n)
  (cond ((= 0 n) 1)
	(t (let ((prod 1))
	     (do ((i 1 (+ i 1)))
		 ((> i n) prod)
	       (set! prod (* prod i)))))))
;;;
;;; Iterative factorial
;;;

(define (fact2 n)
  (cond ((= n 0) 1)
	(#t (do ((i 1 (+ i 1))
		 (prod 1 (* prod i)))
		((> i n) prod)))))
;;;
;;; An alternative way of doing it
;;;

(define (feo l f) ; for each element of a list, do something
  (do ((ls l (cdr ls)))
      ((null? ls))
    (let ((e (car ls)))
      (display (f e)) (display " "))))
;;;
;;; (feo '(1 2 3) odd?)
;;;

(define (for-i from by to f)
  (do ((i from (+ i by)))
      ((> i to))
    (display (f i)) (display " ")))
;;;
;;; (for-i 10 2 20 (lambda (x) (* x x)))
;;;

(define (until p state f)
  (do ((s state (f s)))
      ((p s) s)))
;;;
;;; equivalent of
;;; loop until (p state) do (set! state (f state))
;;; and deliver state as a result
;;;
;;; (until (lambda (x) (> x 100))
;;;         2
;;;        (lambda (x)
;;;	    (display x) (display " ")
;;;	     (* x x)))
;;;
;;; will print out 2 4 16
;;;


(define (case-demo n)
  (case n
    ((0) 'a)
    ((1 3 5 7) 'odd)
    ((2 4 6 8) 'even)
    (else 'dontno)))
;;;
;;; the case statement
;;;