### 4.6.5 Incrementing variables

You can increase the value of a variable a by 4, for
example, with

a := a + 4

If beforehand a were equal to 4, it would now be
equal to 8. A shorthand way of doing this is with the
+= operator;

a += 4

will also increase the value of a by 4.

Similar shorthands exist for subtraction, multiplication and division.
If a is equal to 8 and you enter

then a will be equal to 6. If you follow this with

then a will be equal to 18, and finally

will end with a equal to 2.