Unary Operator

Overview

Unary operator is a prefix operator. Here is the unary operator’s list.

• !, +, -, *, ++, --.
  • ! expression … Operator Not, means it is evaluated as true when expression is false.
  • + expression … Operator Plus, do nothing so far.
  • - expression … Operator Minus, means it makes expression negative when expression is positive.
  • * expression … Operator Asterisk, means it is converted to other type depending on the expression’s type.
  • ++ expression … Operator Plus Plus, means a prefix increment, and the result will be the value after evaluated.
  • -- expression … Operator Minus Minus, means a prefix decrement, and the result will be the value after evaluated.

Note that the true and the false is defined just as Integer of 1 and 0 in Kinx.

var a = false;  // false is just 0 as an integer.
var b = !a;     // b => true, means 1 as an integer.

Examples

Example 1. Simple use of !

Code

System.println(!true);
System.println(!false);
System.println(!True);  // True object.
System.println(!False); // False object.

Result

0
1
0
1

Example 2. Simple use of +

Code

System.println(+true);
System.println(+false);
System.println(+True);  // True object.
System.println(+False); // False object.

Result

1
0
true
false

Example 3. Simple use of -

Code

function test(a) {
    System.println(-a);
}
test(true);
test(false);
test(10);
test(2 ** 70 - 1);

Result

-1
0
-10
-1180591620717411303423

Example 4. Simple use of *

Code

function test(a) {
    System.println(*a);
}
test(97);
test([97, 98, 99]);
test(<97, 98, 99>);
test("ABC");

Result

a
abc
abc
[65, 66, 67]

Example 5. Simple use of ++

Code

function test(a) {
    var b = a;
    System.println([b, ++a]);
}
test(97);
test(2 ** 70);
test(-(2 ** 70));

Result

[97, 98]
[1180591620717411303424, 1180591620717411303425]
[-1180591620717411303424, -1180591620717411303423]

Example 6. Simple use of --

Code

function test(a) {
    var b = a;
    System.println([b, --a]);
}
test(97);
test(2 ** 70);
test(-(2 ** 70));

Result

[97, 96]
[1180591620717411303424, 1180591620717411303423]
[-1180591620717411303424, -1180591620717411303425]