SICP Exercise 1.3: Summing Squares

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

From section 1.1.4 of SICP we already have:

(define (square x) (* x x))
(define (sum-of-squares x y)
  (+ (square x) (square y)))

So all we need to do is determine which of three numbers are the largest two and then evaluate sum-of-squares for those. An alternate way of finding the largest two of three numbers is to find the smallest number - and then the other two numbers are the larger ones. That's how I chose to do it:

(define (sum-of-squares-of-top-two a b c)
  (cond ((and (< a b) (< a c)) (sum-of-squares b c))
        ((and (< b a) (< b c)) (sum-of-squares a c))
        (else (sum-of-squares a b))))

And here it is in action:

> (sum-of-squares-of-top-two 2 3 4)
25
> (sum-of-squares-of-top-two 5 4 3)
41
> (sum-of-squares-of-top-two 6 4 2)
52