(sign n)
  n: a num
  returns an int

Sign.

When (== n 0), returns 0. Otherwise, returns 1 if n is positive, or -1 if n is negative.

This means that the result is always an integer, and the argument -0.0 returns 0 rather than -1. This is usually the more intuitive result. To extract the sign bit from a float, use flo-sign instead.

(sign nan.0) returns 0.