square-root.scm

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

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

(define (sqrt x)

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

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

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

    (sqrt-iter 1.0)
)

(sqrt 9)
(sqrt 2)
(sqrt 0.0001)
(sqrt 9000)