sicp-1.7 created by dcb9 - https://repl.it/KVr5/1

sicp-1.7.sc

(define (average x) (/ x 2))
(define (square x) (* x x))
(define (abs x) (if (< x 0) (- 0 x) x))

; (define (good-enough? guess x)
;   (if (< (abs (- (square guess) x)) 0.00000000001)
;       #t
;       #f))

(define (good-enough? guess x)
  (if (< (/ (abs (- guess (improve guess x))) guess) 0.00000000001)
      #t
      #f))

(define (improve guess x)
  (average (+ (/ x guess) guess)))

(define (sqrt-iter guess x)
  (if (good-enough? guess x)
      guess
      (sqrt-iter (improve guess x) x)))

(define (sqrt x)
  (sqrt-iter 1.0 x))

(sqrt 16)