Third part of SICP exercise 1.3

sicp-1_3-part3.scm

(define (smallest-of-the-two x y)
  (if (<= x y)
      x
      y))

(define (smallest-of-the-two? x y)
  (if (= (smallest-of-the-two x y) x)
      true
      false))

(define (smaller-than-thou x y z)
  (if (and 
       (smallest-of-the-two? x y)
       (smallest-of-the-two? x z))
      x
      false))

(define (smallest-of-the-three a b c)
  (or 
   (smaller-than-thou a b c)
   (smaller-than-thou b a c)
   (smaller-than-thou c a b)))

(define (add-the-two-largest a b c)
  (define remainder (smallest-of-the-three a b c))
  (define subtotal (+ a b c))
  (- subtotal remainder))