haskell-src- Manipulating Haskell source codeSource codeContentsIndex
Class Assertions and Contexts
Variables, Constructors and Operators
Builtin names
Main function of a program
Type constructors
Source coordinates

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.

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]
| HsForeignImport SrcLoc String HsSafety String HsName HsType
| HsForeignExport SrcLoc String String HsName HsType
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 HsSafety
= HsSafe
| HsUnsafe
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
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
data HsModule Source
A Haskell source module.
HsModule SrcLoc Module (Maybe [HsExportSpec]) [HsImportDecl] [HsDecl]
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data HsExportSpec Source
Export specification.
HsEVar HsQNamevariable
HsEAbs HsQNameT: a class or datatype exported abstractly, or a type synonym.
HsEThingAll HsQNameT(..): 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 Modulemodule M: re-export a module.
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data HsImportDecl Source
Import declaration.
importLoc :: SrcLocposition of the import keyword.
importModule :: Modulename of the module imported.
importQualified :: Boolimported qualified?
importAs :: Maybe Moduleoptional 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.
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data HsImportSpec Source
Import specification.
HsIVar HsNamevariable
HsIAbs HsNameT: the name of a class, datatype or type synonym.
HsIThingAll HsNameT(..): 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.
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data HsAssoc Source
Associativity of an operator.
HsAssocNonenon-associative operator (declared with infix)
HsAssocLeftleft-associative operator (declared with infixl).
HsAssocRightright-associative operator (declared with infixr)
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data HsDecl Source
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
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data HsConDecl Source
Declaration of a data constructor.
HsConDecl SrcLoc HsName [HsBangType]ordinary data constructor
HsRecDecl SrcLoc HsName [([HsName], HsBangType)]record constructor
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data HsBangType Source
The type of a constructor argument or field, optionally including a strictness annotation.
HsBangedTy HsTypestrict component, marked with "!"
HsUnBangedTy HsTypenon-strict component
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data HsMatch Source
Clauses of a function binding.
HsMatch SrcLoc HsName [HsPat] HsRhs [HsDecl]
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data HsRhs Source
The right hand side of a function or pattern binding.
HsUnGuardedRhs HsExpunguarded right hand side (exp)
HsGuardedRhss [HsGuardedRhs]guarded right hand side (gdrhs)
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data HsGuardedRhs Source
A guarded right hand side | exp = exp. The first expression will be Boolean-valued.
HsGuardedRhs SrcLoc HsExp HsExp
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data HsSafety Source
Safety level for invoking a foreign entity
HsSafecall may generate callbacks
HsUnsafecall will not generate callbacks
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Class Assertions and Contexts
data HsQualType Source
A type qualified with a context. An unqualified type has an empty context.
HsQualType HsContext HsType
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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.
data HsType Source
Haskell types and type constructors.
HsTyFun HsType HsTypefunction type
HsTyTuple [HsType]tuple type
HsTyApp HsType HsTypeapplication of a type constructor
HsTyVar HsNametype variable
HsTyCon HsQNamenamed type or type constructor
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data HsExp Source

Haskell expressions.


  • 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 Language.Haskell.Pretty.Pretty instance for HsExp does not add parentheses in printing.
HsVar HsQNamevariable
HsCon HsQNamedata constructor
HsLit HsLiteralliteral constant
HsInfixApp HsExp HsQOp HsExpinfix application
HsApp HsExp HsExpordinary application
HsNegApp HsExpnegation expression - exp
HsLambda SrcLoc [HsPat] HsExplambda expression
HsLet [HsDecl] HsExplocal declarations with let
HsIf HsExp HsExp HsExpif 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 HsExpparenthesized expression
HsLeftSection HsExp HsQOpleft section (exp qop)
HsRightSection HsQOp HsExpright section (qop exp)
HsRecConstr HsQName [HsFieldUpdate]record construction expression
HsRecUpdate HsExp [HsFieldUpdate]record update expression
HsEnumFrom HsExpunbounded arithmetic sequence, incrementing by 1
HsEnumFromTo HsExp HsExpbounded arithmetic sequence, incrementing by 1
HsEnumFromThen HsExp HsExpunbounded arithmetic sequence, with first two elements given
HsEnumFromThenTo HsExp HsExp HsExpbounded arithmetic sequence, with first two elements given
HsListComp HsExp [HsStmt]list comprehension
HsExpTypeSig SrcLoc HsExp HsQualTypeexpression type signature
HsAsPat HsName HsExppatterns only
HsWildCardpatterns only
HsIrrPat HsExppatterns only
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data HsStmt Source
This type represents both stmt in a do-expression, and qual in a list comprehension.
HsGenerator SrcLoc HsPat HsExpa generator pat <- exp
HsQualifier HsExpan exp by itself: in a do-expression, an action whose result is discarded; in a list comprehension, a guard expression
HsLetStmt [HsDecl]local bindings
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data HsFieldUpdate Source
An fbind in a labeled record construction or update expression.
HsFieldUpdate HsQName HsExp
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data HsAlt Source
An alt in a case expression.
HsAlt SrcLoc HsPat HsGuardedAlts [HsDecl]
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data HsGuardedAlts Source
HsUnGuardedAlt HsExp-> exp
HsGuardedAlts [HsGuardedAlt]gdpat
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data HsGuardedAlt Source
A guarded alternative | exp -> exp. The first expression will be Boolean-valued.
HsGuardedAlt SrcLoc HsExp HsExp
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data HsPat Source
A pattern, to be matched against a value.
HsPVar HsNamevariable
HsPLit HsLiteralliteral constant
HsPNeg HsPatnegated pattern
HsPInfixApp HsPat HsQName HsPatpattern with infix data constructor
HsPApp HsQName [HsPat]data constructor and argument patterns
HsPTuple [HsPat]tuple pattern
HsPList [HsPat]list pattern
HsPParen HsPatparenthesized pattern
HsPRec HsQName [HsPatField]labelled pattern
HsPAsPat HsName HsPat@-pattern
HsPWildCardwildcard pattern (_)
HsPIrrPat HsPatirrefutable pattern (~)
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data HsPatField Source
An fpat in a labeled record pattern.
HsPFieldPat HsQName HsPat
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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.
HsChar Charcharacter literal
HsString Stringstring literal
HsInt Integerinteger literal
HsFrac Rationalfloating point literal
HsCharPrim CharGHC unboxed character literal
HsStringPrim StringGHC unboxed string literal
HsIntPrim IntegerGHC unboxed integer literal
HsFloatPrim RationalGHC unboxed float literal
HsDoublePrim RationalGHC unboxed double literal
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Variables, Constructors and Operators
newtype Module Source
The name of a Haskell module.
Module String
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data HsQName Source
This type is used to represent qualified variables, and also qualified constructors.
Qual Module HsNamename qualified with a module name
UnQual HsNameunqualified name
Special HsSpecialConbuilt-in constructor with special syntax
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data HsName Source
This type is used to represent variables, and also constructors.
HsIdent Stringvarid or conid
HsSymbol Stringvarsym or consym
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data HsQOp Source
Possibly qualified infix operators (qop), appearing in expressions.
HsQVarOp HsQNamevariable operator (qvarop)
HsQConOp HsQNameconstructor operator (qconop)
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data HsOp Source
Operators, appearing in infix declarations.
HsVarOp HsNamevariable operator (varop)
HsConOp HsNameconstructor operator (conop)
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data HsSpecialCon Source
Constructors with special syntax. These names are never qualified, and always refer to builtin type or data constructors.
HsUnitConunit type and data constructor ()
HsListConlist type constructor []
HsFunConfunction type constructor ->
HsTupleCon Intn-ary tuple type and data constructors (,) etc
HsConslist data constructor (:)
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data HsCName Source
A name (cname) of a component of a class or data type in an import or export specification.
HsVarName HsNamename of a method or field
HsConName HsNamename of a data constructor
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Builtin names
prelude_mod :: ModuleSource
main_mod :: ModuleSource
Main function of a program
main_name :: HsNameSource
unit_con_name :: HsQNameSource
tuple_con_name :: Int -> HsQNameSource
list_cons_name :: HsQNameSource
unit_con :: HsExpSource
tuple_con :: Int -> HsExpSource
Type constructors
unit_tycon_name :: HsQNameSource
fun_tycon_name :: HsQNameSource
list_tycon_name :: HsQNameSource
tuple_tycon_name :: Int -> HsQNameSource
unit_tycon :: HsTypeSource
fun_tycon :: HsTypeSource
list_tycon :: HsTypeSource
tuple_tycon :: Int -> HsTypeSource
Source coordinates
data SrcLoc Source
A position in the source.
srcFilename :: String
srcLine :: Int
srcColumn :: Int
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