Difference between revisions of "GHC/Type system"

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== Type system extensions in GHC ==
 
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[[Category:GHC|Type system]]
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<span style='font-size: x-large; font-weight: bold'>Type system extensions in GHC</span>
   
GHC comes with a rather lare collection of type-system extensions (beyond Haskell 98). They are all documented in the [http://www.haskell.org/ghc/docs/latest/html/users_guide/type-extensions.html user manual], but this page is a place to record observations, notes, and suggestions on them.
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GHC comes with a rather large collection of type-system extensions (beyond Haskell 98). {{GHCUsersGuide|exts||a section on Language Extensions}} But this page is a place to record user-oriented observations, notes, and suggestions on how to use them.
   
=== Overlapping instances ===
 
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* '''[[GHC/Indexed_types|Indexed data types]]'''
 
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* '''[[GHC/TypeHoles|Agda-like "holes" in GHC]]'''
Here an [http://www.haskell.org//pipermail/glasgow-haskell-bugs/2006-July/006808.html interesting message] about the interaction of existential types and overlapping instances.
 
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* '''[[GHC/Stand-alone deriving declarations|"Stand-alone deriving" declarations]]'''
 
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* '''[[GHC/TypeSigsAndAmbiguity|Type signatures and ambiguity]]'''
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* '''Overlapping instances'''. GHC supports overlapping instances, with carefully specified rules. Make sure you read the [http://downloads.haskell.org/~ghc/latest/docs/html/users_guide/exts/instances.html#overlapping-instances relevant sections of the user manual]. Here is an application note about [[GHC/AdvancedOverlap|advanced use of overlapping instances]], combined with functional dependencies.
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* '''[[GHC/SuperClass|Super-Class Constraints: Type Families, Type Equalities, FunDep, Overlaps]]'''
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* '''[[GHC/Coercible|Safe coercions using Coercible]]'''

Latest revision as of 20:32, 23 July 2021

Type system extensions in GHC

GHC comes with a rather large collection of type-system extensions (beyond Haskell 98). The GHC Users Guide has a section on Language Extensions. But this page is a place to record user-oriented observations, notes, and suggestions on how to use them.