scheme learning

guile_install.txt

 
$ sudo aptitude install guile-1.8
$ guile

(trace function-name)
Then, whenever this function is called, it will print a message to the screen showing what arguments it was called with. When the procedure returns, it will print a message showing what value that call returned.
To turn off tracing, use the command:

  (untrace function-name)
Or, to turn off all tracing, simply:
  (untrace)

why_bother_to_use_if.scm

(define (new-if p tc ec) (cond (p tc) (else ec)))

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

(define (sqrt-iter guess x)
  (new-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))

(define (sqrt x)
  (sqrt-iter 1.0 x))
(trace sqrt-iter)
(trace improve) 
(trace good-enough?)
(sqrt 9)

(new-if ( > 5 1) 6 x)
(if (> 5 1) 6 x)

(cond ((> 5 1) 6) (else x))