# User:Zzo38/Proposal for additional kinds

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==New kinds== | ==New kinds== | ||

## -- New name for (#) kind (although (#) is available for compatibility) | ## -- New name for (#) kind (although (#) is available for compatibility) | ||

− | + | & -- Kind for classes | |

+ -- Kind for type-level natural numbers | + -- Kind for type-level natural numbers | ||

$ -- Means make up a kind from a Template Haskell code | $ -- Means make up a kind from a Template Haskell code | ||

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==Kind of classes== | ==Kind of classes== | ||

Example: | Example: | ||

− | + | * -> & -- Kind of Eq class. | |

− | + | (* -> *) -> & -- Kind of Monad class. | |

− | * -> | + | (* -> &) -> & -- Class of classes. |

− | + | + -> * -> & -- Infinite series of classes, selected by a natural number. | |

− | + -> | + | |

− | + | ||

− | + | ||

==Natural number kind== | ==Natural number kind== | ||

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It also means a type of kind <tt>+ -> + -> +</tt> can be a type of adding numbers or other stuff like that, too. | 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>(->)</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]] | [[Category:Proposals]] |

## Latest revision as of 20:18, 12 January 2012

This document is proposal about additional kinds.

## Contents |

## [edit] 1 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

## [edit] 2 Kind of classes

Example:

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

## [edit] 3 Natural number kind

If a type requires a parameter, it can be a `+` 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 `+ -> + -> +` 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 `4` is `Maybe (Maybe (Maybe (Maybe Zero)))`, and `(->)` would be the type for a array with a specific number of elements fixed by the type.