-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
                     an example code for Lisp (scheme)
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

klim@moose> cat sqrt.scm

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

(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))

klim@moose> scheme48 
Welcome to Scheme 48 1.2 (made by klim on Fri Sep 14 19:06:40 CST 2007)
Copyright (c) 1993-2004 by Richard Kelsey and Jonathan Rees.
Please report bugs to scheme-48-bugs@s48.org.
Get more information at http://www.s48.org/.
Type ,? (comma question-mark) for help.
> ,load "sqrt.scm"
> (+ 1 2 3)
6
> (* 2 5 9)
90
> (/ 9 3)
3
> (square 4)
16
> (sqrt 4)
2.0
> (sqrt (square 12.4))
12.4
> (sqrt (square 12.111111))
12.111111
> (sqrt (square 3.141592653))
3.141592653
> 
Exit Scheme 48 (y/n)? y
klim@moose>