Structure and Interpretation of Computer Programs (SICP) - Chapter 1 exercises and solutions in Scheme

chapter1.scm

;; Exercise 1.1. Below is a sequence of expressions. What is the result printed by the interpreter 
;; in response to each expression? Assume that the sequence is to be evaluated in the order in which 
;; it is presented.

10
;Value: 10

(+ 5 3 4)
;Value: 12

(- 9 1)
;Value: 8

(/ 6 2)
;Value: 3

(+ (* 2 4) (- 4 6))
;Value: 6

(define a 3)
;Value: a

(define b (+ a 1))
;Value: b

(+ a b (* a b))
;Value: 19

(= a b)
;Value: #f

(if (and (> b a) (< b (* a b)))
    b
    a)
;Value: 4

(cond ((= a 4) 6)
      ((= b 4) (+ 6 7 a))
      (else 25))
;Value: 16

(+ 2 (if (> b a) b a))
;Value: 6

(* (cond ((> a b) a)
	 ((< a b) b)
	 (else -1))
   (+ a 1))
;Value: 16


;; Exercise 1.2


;; Exercise 1.3. Define a procedure that takes three numbers as arguments and returns the sum of 
;; the squares of the two larger numbers.

(define sum-of-squares
  (lambda (x y z)
    (cond ((> x y)
	   (cond ((> y z) (+ (* x x) (* y y)))
		 (else (+ (* x x) (* z z)))))
	  ((> x z) (+ (* x x) (* y y)))
	  (else (+ (* y y) (* z z))))))

	  
;; Exercise 1.4. Observe that our model of evaluation allows for combinations whose operators are 
;; compound expressions. Use this observation to describe the behavior of the following procedure:

(define (a-plus-abs-b a b)
  ((if (> b 0) + -) a b))