University
of Washington • CSE583 • D. Notkin © 2000
38
Converting to tail recursion
lProgrammers (and sometimes really smart compilers) can sometimes
convert to tail recursion
l(define
(fact n)
(if (= n 0) 1
(+ n
(fact (- n 1))
)))
(if (= n 0) 1
(+ n
(fact (- n 1))
)))
lNot tail recursive
(must do + after
recursive call)
(define (fact n)
(f-iter n 1))
(f-iter n 1))
l(define (f-iter n r)
l (if (= n 0) result
(f-iter
(- n
1)
l (* n result)
)))
•With a helper function, converted to tail recursion