Cabal-1.18.1.2: A framework for packaging Haskell software

Portabilityportable
Maintainer[email protected]
Safe HaskellSafe-Inferred

Language.Haskell.Extension

Description

Haskell language dialects and extensions

Synopsis

Documentation

data Language

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

UnknownLanguage String

An unknown language, identified by its name.

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.

Constructors

EnableExtension KnownExtension

Enable a known extension

DisableExtension KnownExtension

Disable a known extension

UnknownExtension String

An unknown extension, identified by the name of its LANGUAGE pragma.

data KnownExtension

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 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

(deprecated) Allows recursive bindings in do blocks, using the rec keyword. See also RecursiveDo.

RecursiveDo

Allows recursive bindings using mdo, a variant of do. DoRec provides a different, preferred syntax.

ParallelListComp

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

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

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

RankNTypes

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

PolymorphicComponents

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

ExistentialQuantification

Allow existentially-quantified data constructors.

ScopedTypeVariables

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

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 let/where binding.

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 RecordWildCards.

PatternGuards

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

GeneralizedNewtypeDeriving

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

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 # as a postfix modifier on identifiers. Also enables literal syntax for unboxed values.

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 deriving mechanism.

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 foreign import and foreign export.

InterruptibleFFI

Enable interruptible FFI.

CApiFFI

Allow use of CAPI FFI calling convention (foreign import capi).

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.

RecordWildCards

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

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.

GADTSyntax

Enable GADT syntax for declaring ordinary algebraic datatypes.

MonoPatBinds

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

Enable deriving for classes Typeable and Data.

DeriveGeneric

Enable deriving for Generic and Generic1.

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

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.

MultiWayIf

Enable support for multi-way if-expressions.

LambdaCase

Enable support lambda-case expressions.

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 Functor class.

DeriveTraversable

Enable deriving for the Traversable class.

DeriveFoldable

Enable deriving for the Foldable class.

NondecreasingIndentation

Enable non-decreasing indentation for do blocks.

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 (ctxt => ty) syntax so that any type of kind constraint can occur before the arrow.

PolyKinds

Enable kind polymorphism.

DataKinds

Enable datatype promotion.

ParallelArrays

Enable parallel arrays syntax ([:, :]) for Data Parallel Haskell.

RoleAnnotations

Enable explicit role annotations, like in (data T a@R).

OverloadedLists

Enable overloading of list literals, arithmetic sequences and list patterns using the IsList type class.

EmptyCase

Enables case expressions that have no alternatives. Also applies to lambda-case expressions if they are enabled.

AutoDeriveTypeable

Triggers the generation of derived Typeable instances for every datatype and type class declaration.

NegativeLiterals

Desugars negative literals directly (without using negate).

NumDecimals

Allows the use of floating literal syntax for all instances of Num, including Int and Integer.

NullaryTypeClasses

Enables 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.

knownExtensions :: [KnownExtension]

Deprecated: KnownExtension is an instance of Enum and Bounded, use those instead.

deprecatedExtensions :: [(Extension, Maybe Extension)]

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