Portability	portable
Stability	experimental
Maintainer	libraries@haskell.org
Safe Haskell	None

Language.Haskell.Syntax

Contents

Modules
Declarations
Class Assertions and Contexts
Types
Expressions
Patterns
Literals
Variables, Constructors and Operators
Builtin names
Source coordinates

Description

A suite of datatypes describing the abstract syntax of Haskell 98 http://www.haskell.org/onlinereport/ plus a few extensions:

multi-parameter type classes
parameters of type class assertions are unrestricted

This module has been changed so that show is a real show. For GHC, we also derive Typeable and Data for all types.

Synopsis

Modules

data HsModule Source

A Haskell source module.

Constructors

HsModule SrcLoc Module (Maybe [HsExportSpec]) [HsImportDecl] [HsDecl]

Instances

Data HsModule
Show HsModule
Typeable HsModule
Pretty HsModule

data HsExportSpec Source

Export specification.

Constructors

HsEVar HsQName	variable
HsEAbs HsQName	`T`: a class or datatype exported abstractly, or a type synonym.
HsEThingAll HsQName	`T(..)`: a class exported with all of its methods, or a datatype exported with all of its constructors.
HsEThingWith HsQName [HsCName]	`T(C_1,...,C_n)`: a class exported with some of its methods, or a datatype exported with some of its constructors.
HsEModuleContents Module	`module M`: re-export a module.

Instances

Eq HsExportSpec
Data HsExportSpec
Show HsExportSpec
Typeable HsExportSpec
Pretty HsExportSpec

data HsImportDecl Source

Import declaration.

Constructors

HsImportDecl
Fields importLoc :: SrcLoc position of the `import` keyword. importModule :: Module name of the module imported. importQualified :: Bool imported `qualified`? importAs :: Maybe Module optional alias name in an `as` clause. importSpecs :: Maybe (Bool, [HsImportSpec]) optional list of import specifications. The `Bool` is `True` if the names are excluded by `hiding`.

Instances

Eq HsImportDecl
Data HsImportDecl
Show HsImportDecl
Typeable HsImportDecl
Pretty HsImportDecl

data HsImportSpec Source

Import specification.

Constructors

HsIVar HsName	variable
HsIAbs HsName	`T`: the name of a class, datatype or type synonym.
HsIThingAll HsName	`T(..)`: a class imported with all of its methods, or a datatype imported with all of its constructors.
HsIThingWith HsName [HsCName]	`T(C_1,...,C_n)`: a class imported with some of its methods, or a datatype imported with some of its constructors.

Instances

Eq HsImportSpec
Data HsImportSpec
Show HsImportSpec
Typeable HsImportSpec
Pretty HsImportSpec

data HsAssoc Source

Associativity of an operator.

Constructors

HsAssocNone	non-associative operator (declared with `infix`)
HsAssocLeft	left-associative operator (declared with `infixl`).
HsAssocRight	right-associative operator (declared with `infixr`)

Instances

Eq HsAssoc
Data HsAssoc
Show HsAssoc
Typeable HsAssoc
Pretty HsAssoc

Declarations

data HsConDecl Source

Declaration of a data constructor.

Constructors

HsConDecl SrcLoc HsName [HsBangType]	ordinary data constructor
HsRecDecl SrcLoc HsName [([HsName], HsBangType)]	record constructor

Instances

Eq HsConDecl
Data HsConDecl
Show HsConDecl
Typeable HsConDecl
Pretty HsConDecl

data HsBangType Source

The type of a constructor argument or field, optionally including a strictness annotation.

Constructors

HsBangedTy HsType	strict component, marked with "`!`"
HsUnBangedTy HsType	non-strict component

Instances

Eq HsBangType
Data HsBangType
Show HsBangType
Typeable HsBangType
Pretty HsBangType

data HsMatch Source

Clauses of a function binding.

Constructors

HsMatch SrcLoc HsName [HsPat] HsRhs [HsDecl]

Instances

Eq HsMatch
Data HsMatch
Show HsMatch
Typeable HsMatch
Pretty HsMatch

data HsRhs Source

The right hand side of a function or pattern binding.

Constructors

HsUnGuardedRhs HsExp	unguarded right hand side (exp)
HsGuardedRhss [HsGuardedRhs]	guarded right hand side (gdrhs)

Instances

Eq HsRhs
Data HsRhs
Show HsRhs
Typeable HsRhs
Pretty HsRhs

data HsGuardedRhs Source

A guarded right hand side | exp = exp. The first expression will be Boolean-valued.

Constructors

HsGuardedRhs SrcLoc HsExp HsExp

Instances

Eq HsGuardedRhs
Data HsGuardedRhs
Show HsGuardedRhs
Typeable HsGuardedRhs
Pretty HsGuardedRhs

data HsSafety Source

Safety level for invoking a foreign entity

Constructors

HsSafe	call may generate callbacks
HsUnsafe	call will not generate callbacks

Instances

Eq HsSafety
Data HsSafety
Ord HsSafety
Show HsSafety
Typeable HsSafety
Pretty HsSafety

Class Assertions and Contexts

data HsQualType Source

A type qualified with a context. An unqualified type has an empty context.

Constructors

HsQualType HsContext HsType

Instances

Eq HsQualType
Data HsQualType
Show HsQualType
Typeable HsQualType
Pretty HsQualType

type HsContext = [HsAsst]Source

type HsAsst = (HsQName, [HsType])Source

Class assertions. In Haskell 98, the argument would be a tyvar, but this definition allows multiple parameters, and allows them to be types.

Types

data HsType Source

Haskell types and type constructors.

Constructors

HsTyFun HsType HsType	function type
HsTyTuple [HsType]	tuple type
HsTyApp HsType HsType	application of a type constructor
HsTyVar HsName	type variable
HsTyCon HsQName	named type or type constructor

Instances

Eq HsType
Data HsType
Show HsType
Typeable HsType
Pretty HsType

Expressions

data HsExp Source

Haskell expressions.

Notes:

Because it is difficult for parsers to distinguish patterns from expressions, they typically parse them in the same way and then check that they have the appropriate form. Hence the expression type includes some forms that are found only in patterns. After these checks, these constructors should not be used.
The parser does not take precedence and associativity into account, so it will leave HsInfixApps associated to the left.
The Pretty instance for HsExp does not add parentheses in printing.

Constructors

HsVar HsQName	variable
HsCon HsQName	data constructor
HsLit HsLiteral	literal constant
HsInfixApp HsExp HsQOp HsExp	infix application
HsApp HsExp HsExp	ordinary application
HsNegApp HsExp	negation expression `-` exp
HsLambda SrcLoc [HsPat] HsExp	lambda expression
HsLet [HsDecl] HsExp	local declarations with `let`
HsIf HsExp HsExp HsExp	`if` exp `then` exp `else` exp
HsCase HsExp [HsAlt]	`case` exp `of` alts
HsDo [HsStmt]	`do`-expression: the last statement in the list should be an expression.
HsTuple [HsExp]	tuple expression
HsList [HsExp]	list expression
HsParen HsExp	parenthesized expression
HsLeftSection HsExp HsQOp	left section `(`exp qop`)`
HsRightSection HsQOp HsExp	right section `(`qop exp`)`
HsRecConstr HsQName [HsFieldUpdate]	record construction expression
HsRecUpdate HsExp [HsFieldUpdate]	record update expression
HsEnumFrom HsExp	unbounded arithmetic sequence, incrementing by 1
HsEnumFromTo HsExp HsExp	bounded arithmetic sequence, incrementing by 1
HsEnumFromThen HsExp HsExp	unbounded arithmetic sequence, with first two elements given
HsEnumFromThenTo HsExp HsExp HsExp	bounded arithmetic sequence, with first two elements given
HsListComp HsExp [HsStmt]	list comprehension
HsExpTypeSig SrcLoc HsExp HsQualType	expression type signature
HsAsPat HsName HsExp	patterns only
HsWildCard	patterns only
HsIrrPat HsExp	patterns only

Instances

Eq HsExp
Data HsExp
Show HsExp
Typeable HsExp
Pretty HsExp

data HsStmt Source

This type represents both stmt in a do-expression, and qual in a list comprehension.

Constructors

HsGenerator SrcLoc HsPat HsExp	a generator pat `<-` exp
HsQualifier HsExp	an exp by itself: in a `do`-expression, an action whose result is discarded; in a list comprehension, a guard expression
HsLetStmt [HsDecl]	local bindings

Instances

Eq HsStmt
Data HsStmt
Show HsStmt
Typeable HsStmt
Pretty HsStmt

data HsFieldUpdate Source

An fbind in a labeled record construction or update expression.

Constructors

HsFieldUpdate HsQName HsExp

Instances

Eq HsFieldUpdate
Data HsFieldUpdate
Show HsFieldUpdate
Typeable HsFieldUpdate
Pretty HsFieldUpdate

data HsAlt Source

An alt in a case expression.

Constructors

HsAlt SrcLoc HsPat HsGuardedAlts [HsDecl]

Instances

Eq HsAlt
Data HsAlt
Show HsAlt
Typeable HsAlt
Pretty HsAlt

data HsGuardedAlts Source

Constructors

HsUnGuardedAlt HsExp	`->` exp
HsGuardedAlts [HsGuardedAlt]	gdpat

Instances

Eq HsGuardedAlts
Data HsGuardedAlts
Show HsGuardedAlts
Typeable HsGuardedAlts
Pretty HsGuardedAlts

data HsGuardedAlt Source

A guarded alternative | exp -> exp. The first expression will be Boolean-valued.

Constructors

HsGuardedAlt SrcLoc HsExp HsExp

Instances

Eq HsGuardedAlt
Data HsGuardedAlt
Show HsGuardedAlt
Typeable HsGuardedAlt
Pretty HsGuardedAlt

Patterns

data HsPat Source

A pattern, to be matched against a value.

Constructors

HsPVar HsName	variable
HsPLit HsLiteral	literal constant
HsPNeg HsPat	negated pattern
HsPInfixApp HsPat HsQName HsPat	pattern with infix data constructor
HsPApp HsQName [HsPat]	data constructor and argument patterns
HsPTuple [HsPat]	tuple pattern
HsPList [HsPat]	list pattern
HsPParen HsPat	parenthesized pattern
HsPRec HsQName [HsPatField]	labelled pattern
HsPAsPat HsName HsPat	`@`-pattern
HsPWildCard	wildcard pattern (`_`)
HsPIrrPat HsPat	irrefutable pattern (`~`)

Instances

Eq HsPat
Data HsPat
Show HsPat
Typeable HsPat
Pretty HsPat

data HsPatField Source

An fpat in a labeled record pattern.

Constructors

HsPFieldPat HsQName HsPat

Instances

Eq HsPatField
Data HsPatField
Show HsPatField
Typeable HsPatField
Pretty HsPatField

Literals

data HsLiteral Source

literal. Values of this type hold the abstract value of the literal, not the precise string representation used. For example, 10, 0o12 and 0xa have the same representation.

Constructors

HsChar Char	character literal
HsString String	string literal
HsInt Integer	integer literal
HsFrac Rational	floating point literal
HsCharPrim Char	GHC unboxed character literal
HsStringPrim String	GHC unboxed string literal
HsIntPrim Integer	GHC unboxed integer literal
HsFloatPrim Rational	GHC unboxed float literal
HsDoublePrim Rational	GHC unboxed double literal

Instances

Eq HsLiteral
Data HsLiteral
Show HsLiteral
Typeable HsLiteral
Pretty HsLiteral

Variables, Constructors and Operators

newtype Module Source

The name of a Haskell module.

Constructors

Module String

Instances

Eq Module
Data Module
Ord Module
Show Module
Typeable Module
Pretty Module

data HsQName Source

This type is used to represent qualified variables, and also qualified constructors.

Constructors

Qual Module HsName	name qualified with a module name
UnQual HsName	unqualified name
Special HsSpecialCon	built-in constructor with special syntax

Instances

Eq HsQName
Data HsQName
Ord HsQName
Show HsQName
Typeable HsQName
Pretty HsQName

data HsName Source

This type is used to represent variables, and also constructors.

Constructors

HsIdent String	varid or conid
HsSymbol String	varsym or consym

Instances

Eq HsName
Data HsName
Ord HsName
Show HsName
Typeable HsName
Pretty HsName

data HsQOp Source

Possibly qualified infix operators (qop), appearing in expressions.

Constructors

HsQVarOp HsQName	variable operator (qvarop)
HsQConOp HsQName	constructor operator (qconop)

Instances

Eq HsQOp
Data HsQOp
Ord HsQOp
Show HsQOp
Typeable HsQOp
Pretty HsQOp

data HsOp Source

Operators, appearing in infix declarations.

Constructors

HsVarOp HsName	variable operator (varop)
HsConOp HsName	constructor operator (conop)

Instances

Eq HsOp
Data HsOp
Ord HsOp
Show HsOp
Typeable HsOp
Pretty HsOp

data HsSpecialCon Source

Constructors with special syntax. These names are never qualified, and always refer to builtin type or data constructors.

Constructors

HsUnitCon	unit type and data constructor `()`
HsListCon	list type constructor `[]`
HsFunCon	function type constructor `->`
HsTupleCon Int	n-ary tuple type and data constructors `(,)` etc
HsCons	list data constructor `(:)`

Instances

Eq HsSpecialCon
Data HsSpecialCon
Ord HsSpecialCon
Show HsSpecialCon
Typeable HsSpecialCon

data HsCName Source

A name (cname) of a component of a class or data type in an import or export specification.

Constructors

HsVarName HsName	name of a method or field
HsConName HsName	name of a data constructor

Instances

Eq HsCName
Data HsCName
Ord HsCName
Show HsCName
Typeable HsCName
Pretty HsCName

Builtin names

Modules

prelude_mod :: Module Source

main_mod :: Module Source

Main function of a program

main_name :: HsName Source

Constructors

unit_con_name :: HsQName Source

tuple_con_name :: Int -> HsQName Source

list_cons_name :: HsQName Source

unit_con :: HsExp Source

tuple_con :: Int -> HsExp Source

Type constructors

unit_tycon_name :: HsQName Source

fun_tycon_name :: HsQName Source

list_tycon_name :: HsQName Source

tuple_tycon_name :: Int -> HsQName Source

unit_tycon :: HsType Source

fun_tycon :: HsType Source

list_tycon :: HsType Source

tuple_tycon :: Int -> HsType Source

Source coordinates

data SrcLoc Source

A position in the source.

Constructors

SrcLoc
Fields srcFilename :: String srcLine :: Int srcColumn :: Int

Instances

Eq SrcLoc
Data SrcLoc
Ord SrcLoc
Show SrcLoc
Typeable SrcLoc

HsTypeDecl SrcLoc HsName [HsName] HsType
HsDataDecl SrcLoc HsContext HsName [HsName] [HsConDecl] [HsQName]
HsInfixDecl SrcLoc HsAssoc Int [HsOp]
HsNewTypeDecl SrcLoc HsContext HsName [HsName] HsConDecl [HsQName]
HsClassDecl SrcLoc HsContext HsName [HsName] [HsDecl]
HsInstDecl SrcLoc HsContext HsQName [HsType] [HsDecl]
HsDefaultDecl SrcLoc [HsType]
HsTypeSig SrcLoc [HsName] HsQualType
HsFunBind [HsMatch]
HsPatBind SrcLoc HsPat HsRhs [HsDecl]
HsForeignImport SrcLoc String HsSafety String HsName HsType
HsForeignExport SrcLoc String String HsName HsType

Eq HsDecl
Data HsDecl
Show HsDecl
Typeable HsDecl
Pretty HsDecl