Cabal-1.10.1.0: A framework for packaging Haskell software

Portability | portable
Maintainer | libraries@haskell.org

Language.Haskell.Extension

Description

Haskell language dialects and extensions

Synopsis

- data Language
  - = Haskell98
  - | Haskell2010
  - | UnknownLanguage String
- knownLanguages :: [Language]
- data Extension
  - = OverlappingInstances
  - | UndecidableInstances
  - | IncoherentInstances
  - | DoRec
  - | RecursiveDo
  - | ParallelListComp
  - | MultiParamTypeClasses
  - | NoMonomorphismRestriction
  - | FunctionalDependencies
  - | Rank2Types
  - | RankNTypes
  - | PolymorphicComponents
  - | ExistentialQuantification
  - | ScopedTypeVariables
  - | PatternSignatures
  - | ImplicitParams
  - | FlexibleContexts
  - | FlexibleInstances
  - | EmptyDataDecls
  - | CPP
  - | KindSignatures
  - | BangPatterns
  - | TypeSynonymInstances
  - | TemplateHaskell
  - | ForeignFunctionInterface
  - | Arrows
  - | Generics
  - | NoImplicitPrelude
  - | NamedFieldPuns
  - | PatternGuards
  - | GeneralizedNewtypeDeriving
  - | ExtensibleRecords
  - | RestrictedTypeSynonyms
  - | HereDocuments
  - | MagicHash
  - | TypeFamilies
  - | StandaloneDeriving
  - | UnicodeSyntax
  - | UnliftedFFITypes
  - | LiberalTypeSynonyms
  - | TypeOperators
  - | RecordWildCards
  - | RecordPuns
  - | DisambiguateRecordFields
  - | OverloadedStrings
  - | GADTs
  - | NoMonoPatBinds
  - | RelaxedPolyRec
  - | ExtendedDefaultRules
  - | UnboxedTuples
  - | DeriveDataTypeable
  - | ConstrainedClassMethods
  - | PackageImports
  - | ImpredicativeTypes
  - | NewQualifiedOperators
  - | PostfixOperators
  - | QuasiQuotes
  - | TransformListComp
  - | ViewPatterns
  - | XmlSyntax
  - | RegularPatterns
  - | TupleSections
  - | GHCForeignImportPrim
  - | NPlusKPatterns
  - | DoAndIfThenElse
  - | RebindableSyntax
  - | ExplicitForAll
  - | DatatypeContexts
  - | MonoLocalBinds
  - | DeriveFunctor
  - | DeriveTraversable
  - | DeriveFoldable
  - | UnknownExtension String
- knownExtensions :: [Extension]
- deprecatedExtensions :: [(Extension, Maybe Extension)]

# Documentation

data Language

This represents a Haskell language dialect.

Language `Extension`s 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
UnknownLanguage String | An unknown language, identified by its name.

Instances

Eq Language |
Read Language |
Show Language |
Text Language |

knownLanguages :: [Language]

data Extension

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, e.g. "GHC § 7.2.1" for an extension documented in section 7.2.1 of the GHC User's Guide.

Constructors

OverlappingInstances

GHC § 7.6.3.4
  Allow overlapping class instances, provided there is a unique most specific instance for each use.

UndecidableInstances

GHC § 7.6.3.3
  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

GHC § 7.6.3.4
  Implies `OverlappingInstances`. Allow the implementation to choose an instance even when it is possible that further instantiation of types will lead to a more specific instance being applicable.

DoRec

GHC § 7.3.8
  Allows recursive bindings in `do` blocks, using the `rec` keyword.

RecursiveDo

GHC § 7.3.8.2
  Deprecated in GHC. Allows recursive bindings using `mdo`, a variant of `do`. `DoRec` provides a different, preferred syntax.

ParallelListComp

GHC § 7.3.9
  Provide syntax for writing list comprehensions which iterate over several lists together, like the `zipWith` family of functions.

MultiParamTypeClasses

GHC § 7.6.1.1
  Allow multiple parameters in a type class.

NoMonomorphismRestriction

GHC § 7.17
  Disable the dreaded monomorphism restriction.

FunctionalDependencies

GHC § 7.6.2
  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

GHC § 7.8.5
  Like `RankNTypes` but does not allow a higher-rank type to itself appear on the left of a function arrow.

RankNTypes

GHC § 7.8.5
  Allow a universally-quantified type to occur on the left of a function arrow.

PolymorphicComponents

GHC § 7.8.5
  Allow data constructors to have polymorphic arguments. Unlike `RankNTypes`, does not allow this for ordinary functions.

ExistentialQuantification

GHC § 7.4.4
  Allow existentially-quantified data constructors.

ScopedTypeVariables

GHC § 7.8.7
  Cause a type variable in a signature, which has an explicit `forall` quantifier, to scope over the definition of the accompanying value declaration.

PatternSignatures | Deprecated, use `ScopedTypeVariables` instead.

ImplicitParams

GHC § 7.8.3
  Enable implicit function parameters with dynamic scope.

FlexibleContexts

GHC § 7.8.2
  Relax some restrictions on the form of the context of a type signature.

FlexibleInstances

GHC § 7.6.3.2
  Relax some restrictions on the form of the context of an instance declaration.

EmptyDataDecls

GHC § 7.4.1
  Allow data type declarations with no constructors.

CPP

GHC § 4.10.3
  Run the C preprocessor on Haskell source code.

KindSignatures

GHC § 7.8.4
  Allow an explicit kind signature giving the kind of types over which a type variable ranges.

BangPatterns

GHC § 7.11
  Enable a form of pattern which forces evaluation before an attempted match, and a form of strict `let`/`where` binding.

TypeSynonymInstances

GHC § 7.6.3.1
  Allow type synonyms in instance heads.

TemplateHaskell

GHC § 7.9
  Enable Template Haskell, a system for compile-time metaprogramming.

ForeignFunctionInterface

GHC § 8
  Enable the Foreign Function Interface. In GHC, implements the standard Haskell 98 Foreign Function Interface Addendum, plus some GHC-specific extensions.

Arrows

GHC § 7.10
  Enable arrow notation.

Generics

GHC § 7.16
  Enable generic type classes, with default instances defined in terms of the algebraic structure of a type.

NoImplicitPrelude

GHC § 7.3.11
  Disable the implicit importing of the module `Prelude`. When desugaring certain built-in syntax into ordinary identifiers, use whatever is in scope rather than the `Prelude` version.

NamedFieldPuns

GHC § 7.3.15
  Enable syntax for implicitly binding local names corresponding to the field names of a record. Puns bind specific names, unlike `RecordWildCards`.

PatternGuards

GHC § 7.3.5
  Enable a form of guard which matches a pattern and binds variables.

GeneralizedNewtypeDeriving

GHC § 7.5.4
  Allow a type declared with `newtype` to use `deriving` for any class with an instance for the underlying type.

ExtensibleRecords

Hugs § 7.1
  Enable the "Trex" extensible records system.

RestrictedTypeSynonyms

Hugs § 7.2
  Enable type synonyms which are transparent in some definitions and opaque elsewhere, as a way of implementing abstract datatypes.

HereDocuments

Hugs § 7.3
  Enable an alternate syntax for string literals, with string templating.

MagicHash

GHC § 7.3.2
  Allow the character `#` as a postfix modifier on identifiers. Also enables literal syntax for unboxed values.

TypeFamilies

GHC § 7.7
  Allow data types and type synonyms which are indexed by types, i.e. ad-hoc polymorphism for types.

StandaloneDeriving

GHC § 7.5.2
  Allow a standalone declaration which invokes the type class `deriving` mechanism.

UnicodeSyntax

GHC § 7.3.1
  Allow certain Unicode characters to stand for certain ASCII character sequences, e.g. keywords and punctuation.

UnliftedFFITypes

GHC § 8.1.1
  Allow the use of unboxed types as foreign types, e.g. in `foreign import` and `foreign export`.

LiberalTypeSynonyms

GHC § 7.4.3
  Defer validity checking of types until after expanding type synonyms, relaxing the constraints on how synonyms may be used.

TypeOperators

GHC § 7.4.2
  Allow the name of a type constructor, type class, or type variable to be an infix operator.

RecordWildCards

GHC § 7.3.16
  Enable syntax for implicitly binding local names corresponding to the field names of a record. A wildcard binds all unmentioned names, unlike `NamedFieldPuns`.

RecordPuns | Deprecated, use `NamedFieldPuns` instead.

DisambiguateRecordFields

GHC § 7.3.14
  Allow a record field name to be disambiguated by the type of the record it's in.

OverloadedStrings

GHC § 7.6.4
  Enable overloading of string literals using a type class, much like integer literals.

GADTs

GHC § 7.4.6
  Enable generalized algebraic data types, in which type variables may be instantiated on a per-constructor basis. Enables "GADT syntax" which can be used to declare GADTs as well as ordinary algebraic types.

NoMonoPatBinds

GHC § 7.17.2
  Allow pattern bindings to be polymorphic.

RelaxedPolyRec

GHC § 7.8.8
  Relax the requirements on mutually-recursive polymorphic functions.

ExtendedDefaultRules

GHC § 2.4.5
  Allow default instantiation of polymorphic types in more situations.

UnboxedTuples

GHC § 7.2.2
  Enable unboxed tuples.

DeriveDataTypeable

GHC § 7.5.3
  Enable `deriving` for classes `Data.Typeable.Typeable` and `Data.Generics.Data`.

ConstrainedClassMethods

GHC § 7.6.1.3
  Allow a class method's type to place additional constraints on a class type variable.

PackageImports

GHC § 7.3.18
  Allow imports to be qualified by the package name the module is intended to be imported from, e.g.

     import "network" Network.Socket

ImpredicativeTypes

GHC § 7.8.6
  Deprecated in GHC 6.12 and will be removed in GHC 7. Allow a type variable to be instantiated at a polymorphic type.

NewQualifiedOperators

GHC § 7.3.3
  Change the syntax for qualified infix operators.

PostfixOperators

GHC § 7.3.12
  Relax the interpretation of left operator sections to allow unary postfix operators.

QuasiQuotes

GHC § 7.9.5
  Enable quasi-quotation, a mechanism for defining new concrete syntax for expressions and patterns.

TransformListComp

GHC § 7.3.10
  Enable generalized list comprehensions, supporting operations such as sorting and grouping.

ViewPatterns

GHC § 7.3.6
  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 | Enables the use of tuple sections, e.g. `(, True)` desugars into `x -> (x, True)`.
GHCForeignImportPrim | Allows GHC primops, written in C--, to be imported into a Haskell file.
NPlusKPatterns | Support for patterns of the form `n + k`, where `k` is an integer literal.
DoAndIfThenElse | Improve the layout rule when `if` expressions are used in a `do` block.
RebindableSyntax | Makes much of the Haskell sugar be desugared into calls to the function with a particular name that is in scope.
ExplicitForAll | Make `forall` a keyword in types, which can be used to give the generalisation explicitly.
DatatypeContexts | Allow contexts to be put on datatypes, e.g. the `Eq a` in `data Eq a => Set a = NilSet | ConsSet a (Set a)`.
MonoLocalBinds | Local (`let` and `where`) bindings are monomorphic.
DeriveFunctor | Enable `deriving` for the `Data.Functor.Functor` class.
DeriveTraversable | Enable `deriving` for the `Data.Traversable.Traversable` class.
DeriveFoldable | Enable `deriving` for the `Data.Foldable.Foldable` class.
UnknownExtension String | An unknown extension, identified by the name of its `LANGUAGE` pragma.

Instances

Eq Extension |
Read Extension |
Show Extension |
Text Extension |

knownExtensions :: [Extension]

deprecatedExtensions :: [(Extension, Maybe Extension)]

Extensions that have been deprecated, possibly paired with another extension that replaces it.