Difference between revisions of "Language extensions"

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(List of language extensions by name)
 
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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.
 
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 [http://www.haskell.org/ghc/docs/7.0.4/html/users_guide/pragmas.html#language-pragma LANGUAGE pragma] or (in GHC) using the flag -X. The LANGUAGE pragma should be preferred here.
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They can be enabled using the [http://www.haskell.org/ghc/docs/7.0.4/html/users_guide/pragmas.html#language-pragma LANGUAGE pragma]
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<hask>
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{-# LANGUAGE <Extension>, <Extension> #-}
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</hask>
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or (in GHC) using [https://downloads.haskell.org/ghc/latest/docs/html/users_guide/lang.html flags] <code>-X<Extension></code>.
   
 
Before just using the language extension that fits your need, [[Use of language extensions|think about
 
Before just using the language extension that fits your need, [[Use of language extensions|think about
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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]
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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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* [[Rank-N types|RankNTypes]]
 
* [[Rank-N types|RankNTypes]]
 
* [[Scoped type variables|ScopedTypeVariables]]
 
* [[Scoped type variables|ScopedTypeVariables]]
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* [[GHC/Stand-alone_deriving_declarations|StandaloneDeriving]]
 
* [[Template Haskell|TemplateHaskell]]
 
* [[Template Haskell|TemplateHaskell]]
* [http://www.haskell.org/ghc/docs/latest/html/users_guide/syntax-extns.html#tuple-sections TupleSections] : Allow tuples to be partially applied.
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* {{GHCUsersGuide|exts/tuple_sections||section on TupleSections}} It allows tuples to be partially applied.
 
* [[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]
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* [[QualifiedDo]]
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= See also =
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* [[Use of language extensions]]
   
   

Latest revision as of 05:36, 9 September 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