sqrt.scm

来自「这本教材我的导师（国防科大计算机博士）的学习教材」· SCM 代码 · 共 19 行

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

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

(define (sqrt x)
  (define (good-enough? guess x)
    (< (abs (- (square guess) x)) 0.001))
  (define (improve guess x)
    (average guess (/ x guess)))
  (define (sqrt-iter guess x)
    (if (good-enough? guess x)
        guess
        (sqrt-iter (improve guess x) x)))
  (sqrt-iter 1.0 x))

(sqrt 2)
(sqrt 4)
(sqrt 7)