Square root

gistfile1.scm

#lang racket

(define square
  (λ (x)
    (* x x)))

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

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

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

(define check-sqrt
  (λ (guess x)
    (if (is-good-enough guess x)
        guess
        (check-sqrt (improve guess x) x))))

(define sqt
  (λ (x)
    (check-sqrt 1.0 x)))