Logical Operators

Logical operators perform the rough equivalent of a comparison operation on Boolean values. Logical operators use Boolean algebra to evaluate their operands and return the result of the operation. In programming, they are most often used to express complex comparisons which involve multiple operands by linking smaller expressions together.

The following table summarizes the comparison operators available in VectorScript.

 

Operator	Operand	Precedence	Associativity	Operation
NOT	BOOLEAN	1	R-L	Logical NOT
AND	BOOLEAN	7	L-R	Logical AND
&	BOOLEAN	7	L-R	Logical AND (short-circuit)
OR	BOOLEAN	8	L-R	Logical OR
|	BOOLEAN	8	L-R	Logical OR (short-circuit)

Logical NOT ( NOT )

The unary NOT operator is used preceding a single operand of BOOLEAN type to inverts the value of the operand. For example, if a variable z of BOOLEAN type contains the value TRUE, then the expression NOT z will return a value of FALSE. This operation also holds for the results of more complex expressions; for example, if the result of the expression p>=q evaluates to FALSE, the expression NOT(p>=q) will evaluate to TRUE.

Logical AND ( AND )

The AND operator evaluates to TRUE if and only if the first operand and the second operand both are TRUE. If either operand evaluates to FALSE, the result returned will be FALSE. Expressions using the AND operator will always evaluate both operands before returning the result of the expression, regardless of the value of the first operand.

Logical short-circuit AND ( & )

The & operator evaluates to TRUE if and only if the first operand and the second operand are both TRUE. If either operand evaluates to FALSE, the result returned will be FALSE. Expressions using the & operator will not evaluate the second operand if the first operand returns a value of FALSE. If the second operand should have any side effects (such as those produced by a function call returning value) they may not occur. In general, it best to avoid expressions such as the following which combine side effects with the & operator:

(a = b) & SetVectorFill(h,'Stone'){ function call may not occur }

Logical OR ( OR )

The OR operator evaluates to TRUE if the first operand or the second operand are TRUE. Both operands must evaluate to FALSE for the result returned to be FALSE. Expressions using the OR operator will always evaluate both operands before returning the result of the expression, regardless of the value of the first operand.

Logical Short-circuit OR ( | )

The OR operator evaluates to TRUE if the first operand or the second operand are TRUE. Both operands must evaluate to FALSE for the result returned to be FALSE. Expressions using the | operator will not evaluate the second operand if the first operand returns a value of TRUE. If the second operand should have any side effects (such as those produced by a function call returning value) they may not occur. In general, it is best to avoid expressions such as the following which combine side effects with the | operator:

(a = b) | SetVectorFill(h,'Stone') { function call may not occur }