returns a number that indicates the sign of number. The number is first rounded according to standard REXX rules, just as though the operation number+0 had been carried out. Returns -1 if number is less than 0; returns 0 if it is 0; and returns 1 if it is greater than 0.
SIGN('12.3') -> 1
SIGN(' -0.307') -> -1
SIGN(0.0) -> 0