Question

Does Scheme have a sign function? I could not find any information about that.

I define a sign function as a function which produces -1 when x<0, 0 when x=0 and 1 when x>0.

Answer 1

Just use the built-in sgn procedure:

(sgn -10)
=> -1
(sgn 10)
=> 1
(sgn 0)
=> 0

In case you’re wondering how to implement it…

(define (sign n)
  (cond ((negative? n) -1)
        ((positive? n)  1)
        (else 0)))