## 6.5 Constants

constant | ::= | integer-literal
| ∣ | float-literal
| ∣ | char-literal
| ∣ | string-literal
| ∣ | constr
| ∣ | `false`
| ∣ | `true`
| ∣ | `[]`
| ∣ | `()`
| ∣ | ``` tag-name

The syntactic class of constants comprises literals from the four base types (integers, floating-point numbers, characters, character strings), and constant constructors from both normal and polymorphic variants, as well as the special constants `false`, `true`, `[]`, and `()`, which behave like constant constructors.