%BOOL Function
BOOL built-in function returns the boolean value of True or False .
%BOOL (value)
Remarks
Returns boolean value as follows.
- A negative or positive number is true and any value that contains zero is false.
- A string is false if it is zero-length or filled with zeroes only, and true if its length is greater than zero and non-zero characters are present.
- An object of a type other than the four basic types is converted to a boolean in a way that is dependent on that type.