Logical Operators

The Recital/4GL supports the following Logical Operators:

Operator	Operation
.AND./AND	Logical AND
AND	Logical AND
.OR.	Logical OR
OR	Logical OR
.NOT.	Logical NOT
!	Logical NOT
.XOR.	Logical Exclusive OR
XOR	Logical Exclusive OR

If SET OPTLOG or the environment variable DB_OPTLOG are enabled, statements containing Logical Operators are automatically optimized in the following way:

If the Left Hand Side (LHS) of an AND statement is false, then the Right Hand Side (RHS) is parsed, but not evaluated.

If the LHS of an OR statement is TRUE, then the RHS is parsed, but not evaluated.

The above optimizations can be disabled, causing all entries with the statement to be evaluated, if DB_OPTLOG and SET OPTLOG are disabled.

The Logical Operators are evaluated from left to right in the following order:

1. Statements enclosed in parentheses
2. NOT,!
3. AND
4. OR, XOR

Example

? .T. and .F. or .T.
.T.