| Haskell Hierarchical Libraries (haskell-src package) | Contents | Index

Language.Haskell.Syntax

Portability | portable
Stability | experimental
Maintainer | libraries@haskell.org

Contents

Modules
Declarations
Class Assertions and Contexts
Types
Expressions
Patterns
Literals
Variables, Constructors and Operators
Builtin names
  Modules
  Main function of a program
  Constructors
  Special identifiers
  Type constructors
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

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

data HsExportSpec

= HsEVar HsQName
| HsEAbs HsQName
| HsEThingAll HsQName
| HsEThingWith HsQName [HsCName]
| HsEModuleContents Module

data HsImportDecl = HsImportDecl {

importLoc :: SrcLoc
importModule :: Module
importQualified :: Bool
importAs :: (Maybe Module)
importSpecs :: (Maybe (Bool, [HsImportSpec]))

}

data HsImportSpec

= HsIVar HsName
| HsIAbs HsName
| HsIThingAll HsName
| HsIThingWith HsName [HsCName]

data HsAssoc

= HsAssocNone
| HsAssocLeft
| HsAssocRight

data HsDecl

= 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]

data HsConDecl

= HsConDecl SrcLoc HsName [HsBangType]
| HsRecDecl SrcLoc HsName [([HsName], HsBangType)]

data HsBangType

= HsBangedTy HsType
| HsUnBangedTy HsType

data HsMatch = HsMatch SrcLoc HsName [HsPat] HsRhs [HsDecl]

data HsRhs

= HsUnGuardedRhs HsExp
| HsGuardedRhss [HsGuardedRhs]

data HsGuardedRhs = HsGuardedRhs SrcLoc HsExp HsExp
data HsQualType = HsQualType HsContext HsType
type HsContext = [HsAsst]
type HsAsst = (HsQName, [HsType])

data HsType

= HsTyFun HsType HsType
| HsTyTuple [HsType]
| HsTyApp HsType HsType
| HsTyVar HsName
| HsTyCon HsQName

data HsExp

= HsVar HsQName
| HsCon HsQName
| HsLit HsLiteral
| HsInfixApp HsExp HsQOp HsExp
| HsApp HsExp HsExp
| HsNegApp HsExp
| HsLambda SrcLoc [HsPat] HsExp
| HsLet [HsDecl] HsExp
| HsIf HsExp HsExp HsExp
| HsCase HsExp [HsAlt]
| HsDo [HsStmt]
| HsTuple [HsExp]
| HsList [HsExp]
| HsParen HsExp
| HsLeftSection HsExp HsQOp
| HsRightSection HsQOp HsExp
| HsRecConstr HsQName [HsFieldUpdate]
| HsRecUpdate HsExp [HsFieldUpdate]
| HsEnumFrom HsExp
| HsEnumFromTo HsExp HsExp
| HsEnumFromThen HsExp HsExp
| HsEnumFromThenTo HsExp HsExp HsExp
| HsListComp HsExp [HsStmt]
| HsExpTypeSig SrcLoc HsExp HsQualType
| HsAsPat HsName HsExp
| HsWildCard
| HsIrrPat HsExp

data HsStmt

= HsGenerator SrcLoc HsPat HsExp
| HsQualifier HsExp
| HsLetStmt [HsDecl]

data HsFieldUpdate = HsFieldUpdate HsQName HsExp
data HsAlt = HsAlt SrcLoc HsPat HsGuardedAlts [HsDecl]

data HsGuardedAlts

= HsUnGuardedAlt HsExp
| HsGuardedAlts [HsGuardedAlt]

data HsGuardedAlt = HsGuardedAlt SrcLoc HsExp HsExp

data HsPat

= HsPVar HsName
| HsPLit HsLiteral
| HsPNeg HsPat
| HsPInfixApp HsPat HsQName HsPat
| HsPApp HsQName [HsPat]
| HsPTuple [HsPat]
| HsPList [HsPat]
| HsPParen HsPat
| HsPRec HsQName [HsPatField]
| HsPAsPat HsName HsPat
| HsPWildCard
| HsPIrrPat HsPat

data HsPatField = HsPFieldPat HsQName HsPat

data HsLiteral

= HsChar Char
| HsString String
| HsInt Integer
| HsFrac Rational
| HsCharPrim Char
| HsStringPrim String
| HsIntPrim Integer
| HsFloatPrim Rational
| HsDoublePrim Rational

newtype Module = Module String

data HsQName

= Qual Module HsName
| UnQual HsName
| Special HsSpecialCon

data HsName

= HsIdent String
| HsSymbol String

data HsQOp

= HsQVarOp HsQName
| HsQConOp HsQName

data HsOp

= HsVarOp HsName
| HsConOp HsName

data HsSpecialCon

= HsUnitCon
| HsListCon
| HsFunCon
| HsTupleCon Int
| HsCons

data HsCName

= HsVarName HsName
| HsConName HsName

prelude_mod :: Module
main_mod :: Module
main_name :: HsName
unit_con_name :: HsQName
tuple_con_name :: Int -> HsQName
list_cons_name :: HsQName
unit_con :: HsExp
tuple_con :: Int -> HsExp
as_name :: HsName
qualified_name :: HsName
hiding_name :: HsName
minus_name :: HsName
pling_name :: HsName
unit_tycon_name :: HsQName
fun_tycon_name :: HsQName
list_tycon_name :: HsQName
tuple_tycon_name :: Int -> HsQName
unit_tycon :: HsType
fun_tycon :: HsType
list_tycon :: HsType
tuple_tycon :: Int -> HsType

data SrcLoc = SrcLoc {

srcFilename :: String
srcLine :: Int
srcColumn :: Int

}

Modules
data HsModule

A Haskell source module.
Constructors

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

Instances

Data HsModule
Pretty HsModule
Show HsModule
Typeable HsModule

data HsExportSpec

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

Data HsExportSpec
Eq HsExportSpec
Pretty HsExportSpec
Show HsExportSpec
Typeable HsExportSpec

data HsImportDecl

Import declaration.
Constructors

HsImportDecl |

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

Data HsImportDecl
Eq HsImportDecl
Pretty HsImportDecl
Show HsImportDecl
Typeable HsImportDecl

data HsImportSpec

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

Data HsImportSpec
Eq HsImportSpec
Pretty HsImportSpec
Show HsImportSpec
Typeable HsImportSpec

data HsAssoc

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

Data HsAssoc
Eq HsAssoc
Pretty HsAssoc
Show HsAssoc
Typeable HsAssoc

Declarations
data HsDecl

Constructors

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] |

Instances

Data HsDecl
Eq HsDecl
Pretty HsDecl
Show HsDecl
Typeable HsDecl

data HsConDecl

Declaration of a data constructor.
Constructors

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

Instances

Data HsConDecl
Eq HsConDecl
Pretty HsConDecl
Show HsConDecl
Typeable HsConDecl

data HsBangType

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

Data HsBangType
Eq HsBangType
Pretty HsBangType
Show HsBangType
Typeable HsBangType

data HsMatch

Clauses of a function binding.
Constructors

HsMatch SrcLoc HsName [HsPat] HsRhs [HsDecl] |

Instances

Data HsMatch
Eq HsMatch
Pretty HsMatch
Show HsMatch
Typeable HsMatch

data HsRhs

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

Data HsRhs
Eq HsRhs
Pretty HsRhs
Show HsRhs
Typeable HsRhs

data HsGuardedRhs

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

HsGuardedRhs SrcLoc HsExp HsExp |

Instances

Data HsGuardedRhs
Eq HsGuardedRhs
Pretty HsGuardedRhs
Show HsGuardedRhs
Typeable HsGuardedRhs

Class Assertions and Contexts
data HsQualType

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

HsQualType HsContext HsType |

Instances

Data HsQualType
Eq HsQualType
Pretty HsQualType
Show HsQualType
Typeable HsQualType

type HsContext = [HsAsst]
type HsAsst = (HsQName, [HsType])
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

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

Data HsType
Eq HsType
Pretty HsType
Show HsType
Typeable HsType

Expressions
data HsExp

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 `HsInfixApp`s 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

Data HsExp
Eq HsExp
Pretty HsExp
Show HsExp
Typeable HsExp

data HsStmt

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

Data HsStmt
Eq HsStmt
Pretty HsStmt
Show HsStmt
Typeable HsStmt

data HsFieldUpdate

An fbind in a labeled record construction or update expression.
Constructors

HsFieldUpdate HsQName HsExp |

Instances

Data HsFieldUpdate
Eq HsFieldUpdate
Pretty HsFieldUpdate
Show HsFieldUpdate
Typeable HsFieldUpdate

data HsAlt

An alt in a `case` expression.
Constructors

HsAlt SrcLoc HsPat HsGuardedAlts [HsDecl] |

Instances

Data HsAlt
Eq HsAlt
Pretty HsAlt
Show HsAlt
Typeable HsAlt

data HsGuardedAlts

Constructors

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

Instances

Data HsGuardedAlts
Eq HsGuardedAlts
Pretty HsGuardedAlts
Show HsGuardedAlts
Typeable HsGuardedAlts

data HsGuardedAlt

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

HsGuardedAlt SrcLoc HsExp HsExp |

Instances

Data HsGuardedAlt
Eq HsGuardedAlt
Pretty HsGuardedAlt
Show HsGuardedAlt
Typeable HsGuardedAlt

Patterns
data HsPat

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

Data HsPat
Eq HsPat
Pretty HsPat
Show HsPat
Typeable HsPat

data HsPatField

An fpat in a labeled record pattern.
Constructors

HsPFieldPat HsQName HsPat |

Instances

Data HsPatField
Eq HsPatField
Pretty HsPatField
Show HsPatField
Typeable HsPatField

Literals
data HsLiteral

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

Data HsLiteral
Eq HsLiteral
Pretty HsLiteral
Show HsLiteral
Typeable HsLiteral

Variables, Constructors and Operators
newtype Module

The name of a Haskell module.
Constructors

Module String |

Instances

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

data HsQName

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

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

data HsName

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

HsIdent String | varid or conid
HsSymbol String | varsym or consym

Instances

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

data HsQOp

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

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

Instances

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

data HsOp

Operators, appearing in `infix` declarations.
Constructors

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

Instances

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

data HsSpecialCon

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

Data HsSpecialCon
Eq HsSpecialCon
Ord HsSpecialCon
Show HsSpecialCon
Typeable HsSpecialCon

data HsCName

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

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

Builtin names
Modules
prelude_mod :: Module
main_mod :: Module
Main function of a program
main_name :: HsName
Constructors
unit_con_name :: HsQName
tuple_con_name :: Int -> HsQName
list_cons_name :: HsQName
unit_con :: HsExp
tuple_con :: Int -> HsExp
Special identifiers
as_name :: HsName
qualified_name :: HsName
hiding_name :: HsName
minus_name :: HsName
pling_name :: HsName
Type constructors
unit_tycon_name :: HsQName
fun_tycon_name :: HsQName
list_tycon_name :: HsQName
tuple_tycon_name :: Int -> HsQName
unit_tycon :: HsType
fun_tycon :: HsType
list_tycon :: HsType
tuple_tycon :: Int -> HsType
Source coordinates
data SrcLoc

A position in the source.
Constructors

SrcLoc |

srcFilename :: String |
srcLine :: Int |
srcColumn :: Int |

Instances

Data SrcLoc
Eq SrcLoc
Ord SrcLoc
Show SrcLoc
Typeable SrcLoc

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