6.090 IAP '05 Practice Problem Answers

Part 1: Evaluation

1.
14
number

2.
procedure
num->num

3.
procedure
num->num

4.
4
num

5.
7
num

Part 2:

(define (expt x n)
  (if (= n 0)
      1
      (* n (expt x (- n 1)))))

Part 3:

I refuse to do more ascii art.

Part 4:

1.
(define (student-name student)
  (second student))  ; or (cadr student)

2.
(define (student-clue student)
  (fourth student))  ; or (cadddr student)

3.
(define (total-clue list-of-students)
  (if (null? list-of-students)
      0
      (+ (student-clue (car list-of-students))
         (total-clue (cdr list-of-students)))))

4.
(define (average-clue list-of-students)
  (/ (total-clue list-of-students) (length list-of-students)))

Part 5:

1.
recursive

2.
iterative

3.
iterative

4.
recursive