## 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.