| Copyright | Isaac Jones 2003-2004 |
|---|---|
| License | BSD3 |
| Maintainer | libraries@haskell.org |
| Portability | portable |
| Safe Haskell | Safe-Inferred |
| Language | Haskell2010 |
Language.Haskell.Extension
Description
Haskell language dialects and extensions
Synopsis
- data Language
- knownLanguages :: [Language]
- classifyLanguage :: String -> Language
- data Extension
- data KnownExtension
- = OverlappingInstances
- | UndecidableInstances
- | IncoherentInstances
- | DoRec
- | RecursiveDo
- | ParallelListComp
- | MultiParamTypeClasses
- | MonomorphismRestriction
- | FunctionalDependencies
- | Rank2Types
- | RankNTypes
- | PolymorphicComponents
- | ExistentialQuantification
- | ScopedTypeVariables
- | PatternSignatures
- | ImplicitParams
- | FlexibleContexts
- | FlexibleInstances
- | EmptyDataDecls
- | CPP
- | KindSignatures
- | BangPatterns
- | TypeSynonymInstances
- | TemplateHaskell
- | ForeignFunctionInterface
- | Arrows
- | Generics
- | ImplicitPrelude
- | NamedFieldPuns
- | PatternGuards
- | GeneralizedNewtypeDeriving
- | GeneralisedNewtypeDeriving
- | ExtensibleRecords
- | RestrictedTypeSynonyms
- | HereDocuments
- | MagicHash
- | TypeFamilies
- | StandaloneDeriving
- | UnicodeSyntax
- | UnliftedFFITypes
- | InterruptibleFFI
- | CApiFFI
- | LiberalTypeSynonyms
- | TypeOperators
- | RecordWildCards
- | RecordPuns
- | DisambiguateRecordFields
- | TraditionalRecordSyntax
- | OverloadedStrings
- | GADTs
- | GADTSyntax
- | MonoPatBinds
- | RelaxedPolyRec
- | ExtendedDefaultRules
- | UnboxedTuples
- | DeriveDataTypeable
- | DeriveGeneric
- | DefaultSignatures
- | InstanceSigs
- | ConstrainedClassMethods
- | PackageImports
- | ImpredicativeTypes
- | NewQualifiedOperators
- | PostfixOperators
- | QuasiQuotes
- | TransformListComp
- | MonadComprehensions
- | ViewPatterns
- | XmlSyntax
- | RegularPatterns
- | TupleSections
- | GHCForeignImportPrim
- | NPlusKPatterns
- | DoAndIfThenElse
- | MultiWayIf
- | LambdaCase
- | RebindableSyntax
- | ExplicitForAll
- | DatatypeContexts
- | MonoLocalBinds
- | DeriveFunctor
- | DeriveTraversable
- | DeriveFoldable
- | NondecreasingIndentation
- | SafeImports
- | Safe
- | Trustworthy
- | Unsafe
- | ConstraintKinds
- | PolyKinds
- | DataKinds
- | ParallelArrays
- | RoleAnnotations
- | OverloadedLists
- | EmptyCase
- | AutoDeriveTypeable
- | NegativeLiterals
- | BinaryLiterals
- | NumDecimals
- | NullaryTypeClasses
- | ExplicitNamespaces
- | AllowAmbiguousTypes
- | JavaScriptFFI
- | PatternSynonyms
- | PartialTypeSignatures
- | NamedWildCards
- | DeriveAnyClass
- | DeriveLift
- | StaticPointers
- | StrictData
- | Strict
- | ApplicativeDo
- | DuplicateRecordFields
- | TypeApplications
- | TypeInType
- | UndecidableSuperClasses
- | MonadFailDesugaring
- | TemplateHaskellQuotes
- | OverloadedLabels
- | TypeFamilyDependencies
- | DerivingStrategies
- | DerivingVia
- | UnboxedSums
- | HexFloatLiterals
- | BlockArguments
- | NumericUnderscores
- | QuantifiedConstraints
- | StarIsType
- | EmptyDataDeriving
- | CUSKs
- | ImportQualifiedPost
- | StandaloneKindSignatures
- | UnliftedNewtypes
- | LexicalNegation
- | QualifiedDo
- | LinearTypes
- | FieldSelectors
- | OverloadedRecordDot
- | UnliftedDatatypes
- deprecatedExtensions :: [(Extension, Maybe Extension)]
- classifyExtension :: String -> Extension
- knownExtensions :: [KnownExtension]
Documentation
This represents a Haskell language dialect.
Language Extensions are interpreted relative to one of these base
languages.
Constructors
| Haskell98 | The Haskell 98 language as defined by the Haskell 98 report. http://haskell.org/onlinereport/ |
| Haskell2010 | The Haskell 2010 language as defined by the Haskell 2010 report. http://www.haskell.org/onlinereport/haskell2010 |
| GHC2021 | The GHC2021 collection of language extensions. https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0380-ghc2021.rst |
| UnknownLanguage String | An unknown language, identified by its name. |
Instances
knownLanguages :: [Language] Source #
List of known (supported) languages for GHC
classifyLanguage :: String -> Language Source #
This represents language extensions beyond a base Language definition
(such as Haskell98) that are supported by some implementations, usually
in some special mode.
Where applicable, references are given to an implementation's official documentation.
Constructors
| EnableExtension KnownExtension | Enable a known extension |
| DisableExtension KnownExtension | Disable a known extension |
| UnknownExtension String | An unknown extension, identified by the name of its |
Instances
data KnownExtension Source #
Constructors
| OverlappingInstances | Allow overlapping class instances, provided there is a unique most specific instance for each use. |
| UndecidableInstances | Ignore structural rules guaranteeing the termination of class instance resolution. Termination is guaranteed by a fixed-depth recursion stack, and compilation may fail if this depth is exceeded. |
| IncoherentInstances | Implies |
| DoRec | (deprecated) Deprecated in favour of Old description: Allow recursive bindings in |
| RecursiveDo | Allow recursive bindings in |
| ParallelListComp | Provide syntax for writing list comprehensions which iterate
over several lists together, like the |
| MultiParamTypeClasses | Allow multiple parameters in a type class. |
| MonomorphismRestriction | Enable the dreaded monomorphism restriction. |
| FunctionalDependencies | Allow a specification attached to a multi-parameter type class which indicates that some parameters are entirely determined by others. The implementation will check that this property holds for the declared instances, and will use this property to reduce ambiguity in instance resolution. |
| Rank2Types | (deprecated) A synonym for Old description: Like |
| RankNTypes | Allow a universally-quantified type to occur on the left of a function arrow. |
| PolymorphicComponents | (deprecated) A synonym for Old description: Allow data constructors to have polymorphic
arguments. Unlike |
| ExistentialQuantification | Allow existentially-quantified data constructors. |
| ScopedTypeVariables | Cause a type variable in a signature, which has an explicit
|
| PatternSignatures | Deprecated, use |
| ImplicitParams | Enable implicit function parameters with dynamic scope. |
| FlexibleContexts | Relax some restrictions on the form of the context of a type signature. |
| FlexibleInstances | Relax some restrictions on the form of the context of an instance declaration. |
| EmptyDataDecls | Allow data type declarations with no constructors. |
| CPP | Run the C preprocessor on Haskell source code. |
| KindSignatures | Allow an explicit kind signature giving the kind of types over which a type variable ranges. |
| BangPatterns | Enable a form of pattern which forces evaluation before an
attempted match, and a form of strict |
| TypeSynonymInstances | Allow type synonyms in instance heads. |
| TemplateHaskell | Enable Template Haskell, a system for compile-time metaprogramming. |
| ForeignFunctionInterface | Enable the Foreign Function Interface. In GHC, implements the standard Haskell 98 Foreign Function Interface Addendum, plus some GHC-specific extensions. |
| Arrows | Enable arrow notation. |
| Generics | (deprecated) Enable generic type classes, with default instances defined in terms of the algebraic structure of a type. |
| ImplicitPrelude | Enable the implicit importing of the module Prelude. When disabled, when desugaring certain built-in syntax into ordinary identifiers, use whatever is in scope rather than the Prelude -- version. |
| NamedFieldPuns | Enable syntax for implicitly binding local names corresponding
to the field names of a record. Puns bind specific names, unlike
|
| PatternGuards | Enable a form of guard which matches a pattern and binds variables. |
| GeneralizedNewtypeDeriving | Allow a type declared with |
| GeneralisedNewtypeDeriving | |
| ExtensibleRecords | Enable the "Trex" extensible records system. |
| RestrictedTypeSynonyms | Enable type synonyms which are transparent in some definitions and opaque elsewhere, as a way of implementing abstract datatypes. |
| HereDocuments | Enable an alternate syntax for string literals, with string templating. |
| MagicHash | Allow the character |
| TypeFamilies | Allow data types and type synonyms which are indexed by types, i.e. ad-hoc polymorphism for types. |
| StandaloneDeriving | Allow a standalone declaration which invokes the type class
|
| UnicodeSyntax | Allow certain Unicode characters to stand for certain ASCII character sequences, e.g. keywords and punctuation. |
| UnliftedFFITypes | Allow the use of unboxed types as foreign types, e.g. in
|
| InterruptibleFFI | Enable interruptible FFI. |
| CApiFFI | Allow use of CAPI FFI calling convention ( |
| LiberalTypeSynonyms | Defer validity checking of types until after expanding type synonyms, relaxing the constraints on how synonyms may be used. |
| TypeOperators | Allow the name of a type constructor, type class, or type variable to be an infix operator. * https://www.haskell.org/ghc/docs/latest/html/users_guide/glasgow_exts.html#ghc-flag--XTypeOperators |
| RecordWildCards | Enable syntax for implicitly binding local names corresponding
to the field names of a record. A wildcard binds all unmentioned
names, unlike |
| RecordPuns | Deprecated, use |
| DisambiguateRecordFields | Allow a record field name to be disambiguated by the type of the record it's in. |
| TraditionalRecordSyntax | Enable traditional record syntax (as supported by Haskell 98) |
| OverloadedStrings | Enable overloading of string literals using a type class, much like integer literals. |
| GADTs | Enable generalized algebraic data types, in which type
variables may be instantiated on a per-constructor basis. Implies
|
| GADTSyntax | Enable GADT syntax for declaring ordinary algebraic datatypes. |
| MonoPatBinds | (deprecated) Has no effect. Old description: Make pattern bindings monomorphic. |
| RelaxedPolyRec | Relax the requirements on mutually-recursive polymorphic functions. |
| ExtendedDefaultRules | Allow default instantiation of polymorphic types in more situations. |
| UnboxedTuples | Enable unboxed tuples. |
| DeriveDataTypeable | |
| DeriveGeneric | |
| DefaultSignatures | Enable support for default signatures. |
| InstanceSigs | Allow type signatures to be specified in instance declarations. |
| ConstrainedClassMethods | Allow a class method's type to place additional constraints on a class type variable. |
| PackageImports | Allow imports to be qualified by the package name the module is intended to be imported from, e.g. import "network" Network.Socket |
| ImpredicativeTypes | (deprecated) Allow a type variable to be instantiated at a polymorphic type. |
| NewQualifiedOperators | (deprecated) Change the syntax for qualified infix operators. |
| PostfixOperators | Relax the interpretation of left operator sections to allow unary postfix operators. |
| QuasiQuotes | Enable quasi-quotation, a mechanism for defining new concrete syntax for expressions and patterns. |
| TransformListComp | Enable generalized list comprehensions, supporting operations such as sorting and grouping. |
| MonadComprehensions | Enable monad comprehensions, which generalise the list comprehension syntax to work for any monad. |
| ViewPatterns | Enable view patterns, which match a value by applying a function and matching on the result. |
| XmlSyntax | Allow concrete XML syntax to be used in expressions and patterns, as per the Haskell Server Pages extension language: http://www.haskell.org/haskellwiki/HSP. The ideas behind it are discussed in the paper "Haskell Server Pages through Dynamic Loading" by Niklas Broberg, from Haskell Workshop '05. |
| RegularPatterns | Allow regular pattern matching over lists, as discussed in the paper "Regular Expression Patterns" by Niklas Broberg, Andreas Farre and Josef Svenningsson, from ICFP '04. |
| TupleSections | Enable the use of tuple sections, e.g. |
| GHCForeignImportPrim | Allow GHC primops, written in C--, to be imported into a Haskell file. |
| NPlusKPatterns | Support for patterns of the form |
| DoAndIfThenElse | Improve the layout rule when |
| MultiWayIf | Enable support for multi-way |
| LambdaCase | Enable support lambda- |
| RebindableSyntax | Makes much of the Haskell sugar be desugared into calls to the function with a particular name that is in scope. |
| ExplicitForAll | Make |
| DatatypeContexts | Allow contexts to be put on datatypes, e.g. the |
| MonoLocalBinds | Local ( |
| DeriveFunctor | Enable |
| DeriveTraversable | Enable |
| DeriveFoldable | Enable |
| NondecreasingIndentation | Enable non-decreasing indentation for |
| SafeImports | Allow imports to be qualified with a safe keyword that requires the imported module be trusted as according to the Safe Haskell definition of trust. import safe Network.Socket |
| Safe | Compile a module in the Safe, Safe Haskell mode -- a restricted form of the Haskell language to ensure type safety. |
| Trustworthy | Compile a module in the Trustworthy, Safe Haskell mode -- no restrictions apply but the module is marked as trusted as long as the package the module resides in is trusted. |
| Unsafe | Compile a module in the Unsafe, Safe Haskell mode so that modules compiled using Safe, Safe Haskell mode can't import it. |
| ConstraintKinds | Allow type classimplicit parameterequality constraints to be
used as types with the special kind constraint. Also generalise
the |
| PolyKinds | Enable kind polymorphism. |
| DataKinds | Enable datatype promotion. |
| ParallelArrays | Enable parallel arrays syntax ( |
| RoleAnnotations | Enable explicit role annotations, like in ( |
| OverloadedLists | Enable overloading of list literals, arithmetic sequences and
list patterns using the |
| EmptyCase | Enable case expressions that have no alternatives. Also applies to lambda-case expressions if they are enabled. |
| AutoDeriveTypeable | (deprecated) Deprecated in favour of Old description: Triggers the generation of derived |
| NegativeLiterals | Desugars negative literals directly (without using negate). |
| BinaryLiterals | Allow the use of binary integer literal syntax (e.g. |
| NumDecimals | Allow the use of floating literal syntax for all instances of |
| NullaryTypeClasses | Enable support for type classes with no type parameter. |
| ExplicitNamespaces | Enable explicit namespaces in module import/export lists. |
| AllowAmbiguousTypes | Allow the user to write ambiguous types, and the type inference engine to infer them. |
| JavaScriptFFI | Enable |
| PatternSynonyms | Allow giving names to and abstracting over patterns. |
| PartialTypeSignatures | Allow anonymous placeholders (underscore) inside type signatures. The type inference engine will generate a message describing the type inferred at the hole's location. |
| NamedWildCards | Allow named placeholders written with a leading underscore inside type signatures. Wildcards with the same name unify to the same type. |
| DeriveAnyClass | Enable |
| DeriveLift | Enable |
| StaticPointers | Enable support for 'static pointers' (and the |
| StrictData | Switches data type declarations to be strict by default (as if
they had a bang using |
| Strict | Switches all pattern bindings to be strict by default (as if
they had a bang using |
| ApplicativeDo | Allows |
| DuplicateRecordFields | Allow records to use duplicated field labels for accessors. |
| TypeApplications | Enable explicit type applications with the syntax |
| TypeInType | Dissolve the distinction between types and kinds, allowing the compiler to reason about kind equality and therefore enabling GADTs to be promoted to the type-level. |
| UndecidableSuperClasses | Allow recursive (and therefore undecidable) super-class relationships. |
| MonadFailDesugaring | A temporary extension to help library authors check if their code will compile with the new planned desugaring of fail. |
| TemplateHaskellQuotes | A subset of |
| OverloadedLabels | Allows use of the |
| TypeFamilyDependencies | Allow functional dependency annotations on type families to declare them as injective. |
| DerivingStrategies | Allow multiple |
| DerivingVia | Enable deriving instances via types of the same runtime representation.
Implies |
| UnboxedSums | Enable the use of unboxed sum syntax. |
| HexFloatLiterals | Allow use of hexadecimal literal notation for floating-point values. |
| BlockArguments | Allow |
| NumericUnderscores | Allow use of underscores in numeric literals. |
| QuantifiedConstraints | Allow |
| StarIsType | Have |
| EmptyDataDeriving | Liberalises deriving to provide instances for empty data types. |
| CUSKs | Enable detection of complete user-supplied kind signatures. |
| ImportQualifiedPost | Allows the syntax |
| StandaloneKindSignatures | Allow the use of standalone kind signatures. |
| UnliftedNewtypes | Enable unlifted newtypes. |
| LexicalNegation | Use whitespace to determine whether the minus sign stands for negation or subtraction. |
| QualifiedDo | Enable qualified do-notation desugaring. |
| LinearTypes | Enable linear types. |
| FieldSelectors | Enable the generation of selector functions corresponding to record fields. |
| OverloadedRecordDot | Enable the use of record dot-accessor and updater syntax |
| UnliftedDatatypes | Enable data types for which an unlifted or levity-polymorphic result kind is inferred. |
Instances
deprecatedExtensions :: [(Extension, Maybe Extension)] Source #
Extensions that have been deprecated, possibly paired with another extension that replaces it.
classifyExtension :: String -> Extension Source #