anchor.diff:  ;; Common Lisp Script
   ;; Manoel Vilela
   
  -#| A heuristic method to calculate the 
  -   square root of a number x based on the 
  +#| A heuristic method to calculate the
  +   square root of a number x based on the
      Hero of Alexandria's alogrithm.
    |#
   
  - 
  +
   (defparameter *error-limit* 0.001)
   
   (defparameter *tests* '((square-root 2)
  
positive.code:       (format t "Tests avalied [pass/total]: ~d/~d ~%" pass total)))
  
  
  (run-tests)
negative.code: (defun square (x)
    (* x x))
  
  (defun average (x y)
    (/ (+ x y) 2))
  
  ;; square-root black box
  ;; functional by function composition
  (defun square-root (x &key (error-limit *error-limit*))
    (labels ((improve (guess)
               (average guess (/ x guess)))
             (good-enough? (guess)
  