impossible to know if they are equal. Chapter 3. NULL in operations 9 Here is the complete list of math and string operators that return NULL if at least one operand is NULL: • +, -, *, and / • !=, ~= left- hand side expression is NULL. This follows from the definitions and the rules of formal logic. (Math- heads will already have noticed that ALL is equivalent to the universal (“A”) quantifier and ANY|SOME (UDFs)�), it’s still wrong. Incorrect results are returned and this should not happen. Most of the math functions in ib_udf, as well as some others, have this bug. UDFs returning NULL when they should