## 6.5 Constants

constant | ::= | integer-literal
| ∣ | float-literal
| ∣ | char-literal
| ∣ | string-literal
| ∣ | constr
| ∣ | false
| ∣ | true
| ∣ | ()
| ∣ | begin end
| ∣ | []
| ∣ | [||]
| ∣ | `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, and begin end, which is equivalent to ().