Examples (Blackboard)

(absolute-value (+ x 3))

((lambda (a) (* a a)) (+ 2 3))

(define sum-digits
  (lambda (n)
    (if (< n 10)
        n
        (+ (remainder n 10)
           (sum-digits (quotient n 10))))))

(define cast-nines
  (lambda (n)
    (cond ((= n 9) 0)
          ((< n 9) n)
          (else (cast-nines (sum-digits n))))))

Jim Miller