====== SGN ======

The ''SGN()'' function returns the sign of a numerical argument as follows:

^Argument^Result^
|negative value|-1|
|zero|0|
|positive value (excluding zero)| 1|

===== Function header =====

  DECLARE FUNCTION SGN AS INT (num AS BYTE) SHARED STATIC INLINE
  DECLARE FUNCTION SGN AS INT (num AS INT) OVERLOAD SHARED STATIC INLINE
  DECLARE FUNCTION SGN AS INT (num AS WORD) OVERLOAD SHARED STATIC INLINE
  DECLARE FUNCTION SGN AS INT (num AS LONG) OVERLOAD SHARED STATIC INLINE
  DECLARE FUNCTION SGN AS INT (num AS FLOAT) OVERLOAD SHARED STATIC INLINE