|
A
unary expression returns different results depending on which of
the unary operators is used.
Expression
|
Character representation
|
Returns
|
|---|
Unary
|
-
|
The arithmetic negation of the operand,
or null if the operand is null.
|
|
+
|
The arithmetic value of the operand (unchanged),
or null if its operand is null.
|
|
not
|
The logical negation of the operand.
|
Note: The arithmetic negation of a null operand yields
the result null, whereas the logical negation of a null operand
yields the Boolean result true. This is justified by the common
sense statement: If null means nothing, then “not nothing” should
be something.
These are examples of using the unary expression:
Expression
|
Returns
|
|---|
-(17)
|
-17
|
-(-17)
|
17
|
+(17)
|
17
|
+(-17)
|
-17
|
not("true")
|
1 (true)
|
not(1)
|
0 (false)
|
|
|
|
