Data.Unit

data Unit

The Unit type has a single inhabitant, called unit. It represents values with no computational content.

Unit is often used, wrapped in a monadic type constructor, as the return type of a computation where only the effects are important.

When returning a value of type Unit from an FFI function, it is recommended to use undefined, or not return a value at all.

unit :: Unit

unit is the sole inhabitant of the Unit type.