Difference between revisions of "Language extensions"

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(fix link to tuple sections)
(fix links to ghc user guide)
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* [[Default signatures|DefaultSignatures]]
 
* [[Default signatures|DefaultSignatures]]
 
* Derive:
 
* Derive:
** [http://www.haskell.org/ghc/docs/latest/html/users_guide/deriving.html#deriving-typeable DeriveDataTypeable]
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** [https://downloads.haskell.org/~ghc/8.10.3/docs/html/users_guide/glasgow_exts.html#deriving-typeable-instances DeriveDataTypeable]
** [http://www.haskell.org/ghc/docs/latest/html/users_guide/deriving.html#deriving-typeable DeriveGeneric]
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** [https://downloads.haskell.org/~ghc/8.10.3/docs/html/users_guide/glasgow_exts.html#extension-DeriveGeneric DeriveGeneric]
** [http://www.haskell.org/ghc/docs/latest/html/users_guide/deriving.html#deriving-typeable DeriveFunctor]
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** [https://downloads.haskell.org/~ghc/8.10.3/docs/html/users_guide/glasgow_exts.html#extension-DeriveFunctor DeriveFunctor]
** [http://www.haskell.org/ghc/docs/latest/html/users_guide/deriving.html#deriving-typeable DeriveFoldable]
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** [https://downloads.haskell.org/~ghc/8.10.3/docs/html/users_guide/glasgow_exts.html#extension-DeriveFoldable DeriveFoldable]
** [http://www.haskell.org/ghc/docs/latest/html/users_guide/deriving.html#deriving-typeable DeriveTraversable]
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** [https://downloads.haskell.org/~ghc/8.10.3/docs/html/users_guide/glasgow_exts.html#extension-DeriveTraversable DeriveTraversable]
** [http://www.haskell.org/ghc/docs/latest/html/users_guide/deriving.html#id616911 GeneralizedNewtypeDeriving]
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** [https://downloads.haskell.org/~ghc/8.10.3/docs/html/users_guide/glasgow_exts.html#extension-GeneralizedNewtypeDeriving GeneralizedNewtypeDeriving]
* [https://downloads.haskell.org/ghc/latest/docs/html/users_guide/glasgow_exts.html#duplicate-record-fields DuplicateRecordFields] (GHC 8.0.1+) : Allow definition of record types with identically-named fields.
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* [https://downloads.haskell.org/~ghc/8.10.3/docs/html/users_guide/glasgow_exts.html#extension-DuplicateRecordFields DuplicateRecordFields] (GHC 8.0.1+) : Allow definition of record types with identically-named fields.
 
* [[Existential type|ExistentialQuantification]]
 
* [[Existential type|ExistentialQuantification]]
 
* [[Flexible contexts|FlexibleContexts]]
 
* [[Flexible contexts|FlexibleContexts]]
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* [[GHC/Type families|TypeFamilies]]
 
* [[GHC/Type families|TypeFamilies]]
 
* [[Undecidable instance|UndecidableInstances]]
 
* [[Undecidable instance|UndecidableInstances]]
* [http://www.haskell.org/ghc/docs/latest/html/users_guide/syntax-extns.html#view-patterns ViewPatterns]
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* [https://downloads.haskell.org/~ghc/8.10.3/docs/html/users_guide/glasgow_exts.html#extension-ViewPatterns ViewPatterns]
 
* [[QualifiedDo]]
 
* [[QualifiedDo]]
   

Revision as of 18:45, 3 February 2021

Language extensions are used to enable language features in Haskell that may seem useful in certain cases. They can be used to loosen restrictions in the type system or add completely new language constructs to Haskell.

They can be enabled using the LANGUAGE pragma

{-# LANGUAGE <Extension>, <Extension> #-}

or (in GHC) using flags -X<Extension>.

Before just using the language extension that fits your need, think about when it is useful and what risk it may bring to your program.

List of language extensions by name

This list is far from complete and needs extension.

See also