1.1.7.rkt

#lang racket

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


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


(define (average x y)
  (/ (+ x y) 2))


(define (good-enough? guess x)
  (< (abs (- (square guess) x)) 0.001))


(define (abs x)
  (if (> x 0) x (- x)))


(define (square x)
  (* x x))


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


(sqrt 2)
; Value: 1.4142156862745097