# User:Zzo38/Proposal for additional kinds

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==New kinds== |
==New kinds== |
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## -- New name for (#) kind (although (#) is available for compatibility) |
## -- New name for (#) kind (although (#) is available for compatibility) |
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− | [x] -- If x is a kind, [x] is the kind of classes of types of kind x |
+ | & -- Kind for classes |

+ -- Kind for type-level natural numbers |
+ -- Kind for type-level natural numbers |
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+ | $ -- Means make up a kind from a Template Haskell code |
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==Kind of classes== |
==Kind of classes== |
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Example: |
Example: |
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− | [*] -- Kind of Eq class. |
+ | * -> & -- Kind of Eq class. |

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

− | * -> [*] -- A class that requires a type as a parameter to make a class. |
+ | (* -> &) -> & -- Class of classes. |

− | [<b></b>[*]] -- Class of classes. |
+ | + -> * -> & -- Infinite series of classes, selected by a natural number. |

− | <!-- <b></b> means make it appear correctly on HTML view --> |
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==Natural number kind== |
==Natural number kind== |
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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. |
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. |
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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. |
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+ | |||

+ | 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. |
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+ | |||

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