Boolean values

### 4.1.1 Boolean values

The symbols true and false are booleans, and are meant to indicate a statement is true or false.

These constants have synonyms:

- true is the same as TRUE.
- false is the same as FALSE.
- true and false are both integers with values 1 and 0, respectively, but have a different subtype than ordinary integers to indicate that they are boolean values.

A function which returns a boolean is called a test (or a condition or a boolean function).