View source for User:Zzo38/Proposal for additional kinds

This document is proposal about additional kinds.

==New kinds==
 ##      -- New name for (#) kind (although (#) is available for compatibility)
 &       -- Kind for classes
 +       -- Kind for type-level natural numbers
 $       -- Means make up a kind from a Template Haskell code

==Kind of classes==
Example:
 * -> & -- Kind of Eq class.
 (* -> *) -> & -- Kind of Monad class.
 (* -> &) -> & -- Class of classes.
 + -> * -> & -- Infinite series of classes, selected by a natural number.

==Natural number kind==
If a type requires a parameter, it can be a <tt>+</tt> kind, meaning numbers.

There should be some way to specify a type taking natural numbers by defining it for zero and them for a successor, so that it applies for all natural numbers.

It also means a type of kind <tt>+ -> + -> +</tt> can be a type of adding numbers or other stuff like that, too.

A natural number type would be a type with the number of values being that number, for example <tt>4</tt> is <tt>Maybe (Maybe (Maybe (Maybe Zero)))</tt>, and <tt>(-&gt;)</tt> would be the type for a array with a specific number of elements fixed by the type.

==See also==
* [http://hackage.haskell.org/trac/ghc/wiki/KindFact KindFact]

[[Category:Proposals]]