Unit type

With unit type ( English unit type ) is called in the type theory and computer science to those type that only has a single value.

The terms of the type range (eg Scala) and void (C and derivatives depending on the area of 1 ( category theory ) over () ( Haskell ) to Unit; are here, however, the correspondence is not complete, since void is not used anywhere may, where one type is required, and because literals missing).

Since there is only one value, it carries no information with it. If it is necessary to designate the value 0 as this is often - tuple (), or with a symbol as used otherwise.