The not() function returns the logical inverse of the normal outcome of true and false generated by a logical expression.
not(logical.exp)
logical.exp | Expression to test. |
If the expression evaluates to 0, then 1 is returned. If the expression evaluates to any nonzero value, 0 is returned.
If response is not numeric, this prints "not numeric".
if not(num(response)) then print "not numeric"