    {-# OPTIONS_GHC -fglasgow-exts -cpp #-}
    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Language.Haskell.Syntax
    -- Copyright   :  (c) The GHC Team, 1997-2000
    -- License     :  BSD-style (see the file libraries/base/LICENSE)
    --
    -- Maintainer  :  libraries@haskell.org
    -- Stability   :  experimental
    -- Portability :  portable
    --
    -- 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.

    -----------------------------------------------------------------------------

    module Language.Haskell.Syntax (
        -- * Modules
        HsModule(..), HsExportSpec(..),
        HsImportDecl(..), HsImportSpec(..), HsAssoc(..),
        -- * Declarations
        HsDecl(..), HsConDecl(..), HsBangType(..),
        HsMatch(..), HsRhs(..), HsGuardedRhs(..),
        HsSafety(..),
        -- * Class Assertions and Contexts
        HsQualType(..), HsContext, HsAsst,
        -- * Types
        HsType(..),
        -- * Expressions
        HsExp(..), HsStmt(..), HsFieldUpdate(..),
        HsAlt(..), HsGuardedAlts(..), HsGuardedAlt(..),
        -- * Patterns
        HsPat(..), HsPatField(..),
        -- * Literals
        HsLiteral(..),
        -- * Variables, Constructors and Operators
        Module(..), HsQName(..), HsName(..), HsQOp(..), HsOp(..),
        HsSpecialCon(..), HsCName(..),

        -- * Builtin names

        -- ** Modules
        prelude_mod, main_mod,
        -- ** Main function of a program
        main_name,
        -- ** Constructors
        unit_con_name, tuple_con_name, list_cons_name,
        unit_con, tuple_con,
        -- ** Type constructors
        unit_tycon_name, fun_tycon_name, list_tycon_name, tuple_tycon_name,
        unit_tycon, fun_tycon, list_tycon, tuple_tycon,

        -- * Source coordinates
        SrcLoc(..),
      ) where

    #ifdef __GLASGOW_HASKELL__
    import Data.Generics.Basics
    import Data.Generics.Instances()
    #endif

    -- | A position in the source.
    data SrcLoc = SrcLoc {
    		srcFilename :: String,
    		srcLine :: Int,
    		srcColumn :: Int
    		}
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Ord,Show,Typeable,Data)
    #else
      deriving (Eq,Ord,Show)
    #endif

    -- | The name of a Haskell module.
    newtype Module = Module String
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Ord,Show,Typeable,Data)
    #else
      deriving (Eq,Ord,Show)
    #endif

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

    data HsSpecialCon
    	= 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 @(:)@
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Ord,Show,Typeable,Data)
    #else
      deriving (Eq,Ord,Show)
    #endif

    -- | This type is used to represent qualified variables, and also
    -- qualified constructors.
    data HsQName
    	= Qual Module HsName	-- ^ name qualified with a module name
    	| UnQual HsName		-- ^ unqualified name
    	| Special HsSpecialCon	-- ^ built-in constructor with special syntax
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Ord,Show,Typeable,Data)
    #else
      deriving (Eq,Ord,Show)
    #endif

    -- | This type is used to represent variables, and also constructors.
    data HsName
    	= HsIdent String	-- ^ /varid/ or /conid/
    	| HsSymbol String	-- ^ /varsym/ or /consym/
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Ord,Show,Typeable,Data)
    #else
      deriving (Eq,Ord,Show)
    #endif

    -- | Possibly qualified infix operators (/qop/), appearing in expressions.
    data HsQOp
    	= HsQVarOp HsQName	-- ^ variable operator (/qvarop/)
    	| HsQConOp HsQName	-- ^ constructor operator (/qconop/)
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Ord,Show,Typeable,Data)
    #else
      deriving (Eq,Ord,Show)
    #endif

    -- | Operators, appearing in @infix@ declarations.
    data HsOp
    	= HsVarOp HsName	-- ^ variable operator (/varop/)
    	| HsConOp HsName	-- ^ constructor operator (/conop/)
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Ord,Show,Typeable,Data)
    #else
      deriving (Eq,Ord,Show)
    #endif

    -- | A name (/cname/) of a component of a class or data type in an @import@
    -- or export specification.
    data HsCName
    	= HsVarName HsName	-- ^ name of a method or field
    	| HsConName HsName	-- ^ name of a data constructor
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Ord,Show,Typeable,Data)
    #else
      deriving (Eq,Ord,Show)
    #endif

    -- | A Haskell source module.
    data HsModule = HsModule SrcLoc Module (Maybe [HsExportSpec])
                             [HsImportDecl] [HsDecl]
    #ifdef __GLASGOW_HASKELL__
      deriving (Show,Typeable,Data)
    #else
      deriving (Show)
    #endif

    -- | Export specification.
    data HsExportSpec
    	 = 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.
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | Import declaration.
    data HsImportDecl = 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@.
    	}
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | Import specification.
    data HsImportSpec
    	 = 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.
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | Associativity of an operator.
    data HsAssoc
    	 = HsAssocNone	-- ^ non-associative operator (declared with @infix@)
    	 | HsAssocLeft	-- ^ left-associative operator (declared with @infixl@).
    	 | HsAssocRight	-- ^ right-associative operator (declared with @infixr@)
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    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 {-where-} [HsDecl]
    	 | HsForeignImport SrcLoc String HsSafety String HsName HsType
    	 | HsForeignExport SrcLoc String String HsName HsType
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | Clauses of a function binding.
    data HsMatch
    	 = HsMatch SrcLoc HsName [HsPat] HsRhs {-where-} [HsDecl]
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | Declaration of a data constructor.
    data HsConDecl
    	 = HsConDecl SrcLoc HsName [HsBangType]
    				-- ^ ordinary data constructor
    	 | HsRecDecl SrcLoc HsName [([HsName],HsBangType)]
    				-- ^ record constructor
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | The type of a constructor argument or field, optionally including
    -- a strictness annotation.
    data HsBangType
    	 = HsBangedTy   HsType	-- ^ strict component, marked with \"@!@\"
    	 | HsUnBangedTy HsType	-- ^ non-strict component
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | The right hand side of a function or pattern binding.
    data HsRhs
    	 = HsUnGuardedRhs HsExp	-- ^ unguarded right hand side (/exp/)
    	 | HsGuardedRhss  [HsGuardedRhs]
    				-- ^ guarded right hand side (/gdrhs/)
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | A guarded right hand side @|@ /exp/ @=@ /exp/.
    -- The first expression will be Boolean-valued.
    data HsGuardedRhs
    	 = HsGuardedRhs SrcLoc HsExp HsExp
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- ^ Safety level for invoking a foreign entity
    data HsSafety
    	= HsSafe	-- ^ call may generate callbacks
    	| HsUnsafe	-- ^ call will not generate callbacks
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Ord,Show,Typeable,Data)
    #else
      deriving (Eq,Ord,Show)
    #endif

    -- | A type qualified with a context.
    --   An unqualified type has an empty context.
    data HsQualType
    	 = HsQualType HsContext HsType
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | Haskell types and type constructors.
    data HsType
    	 = 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
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    type HsContext = [HsAsst]

    -- | Class assertions.
    --   In Haskell 98, the argument would be a /tyvar/, but this definition
    --   allows multiple parameters, and allows them to be /type/s.
    type HsAsst    = (HsQName,[HsType])

    -- | /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.
    data HsLiteral
    	= 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
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | 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 'Language.Haskell.Pretty.Pretty' instance for 'HsExp' does not
    --   add parentheses in printing.

    data HsExp
    	= 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
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | A pattern, to be matched against a value.
    data HsPat
    	= 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 (@~@)
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | An /fpat/ in a labeled record pattern.
    data HsPatField
    	= HsPFieldPat HsQName HsPat
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | This type represents both /stmt/ in a @do@-expression,
    --   and /qual/ in a list comprehension.
    data HsStmt
    	= 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
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | An /fbind/ in a labeled record construction or update expression.
    data HsFieldUpdate
    	= HsFieldUpdate HsQName HsExp
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | An /alt/ in a @case@ expression.
    data HsAlt
    	= HsAlt SrcLoc HsPat HsGuardedAlts [HsDecl]
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    data HsGuardedAlts
    	= HsUnGuardedAlt HsExp		-- ^ @->@ /exp/
    	| HsGuardedAlts  [HsGuardedAlt]	-- ^ /gdpat/
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -- | A guarded alternative @|@ /exp/ @->@ /exp/.
    -- The first expression will be Boolean-valued.
    data HsGuardedAlt
    	= HsGuardedAlt SrcLoc HsExp HsExp
    #ifdef __GLASGOW_HASKELL__
      deriving (Eq,Show,Typeable,Data)
    #else
      deriving (Eq,Show)
    #endif

    -----------------------------------------------------------------------------
    -- Builtin names.

    prelude_mod, main_mod :: Module
    prelude_mod	      = Module "Prelude"
    main_mod	      = Module "Main"

    main_name :: HsName
    main_name	      = HsIdent "main"

    unit_con_name :: HsQName
    unit_con_name	      = Special HsUnitCon

    tuple_con_name :: Int -> HsQName
    tuple_con_name i      = Special (HsTupleCon (i+1))

    list_cons_name :: HsQName
    list_cons_name	      = Special HsCons

    unit_con :: HsExp
    unit_con	      = HsCon unit_con_name

    tuple_con :: Int -> HsExp
    tuple_con i	      = HsCon (tuple_con_name i)

    unit_tycon_name, fun_tycon_name, list_tycon_name :: HsQName
    unit_tycon_name       = unit_con_name
    fun_tycon_name        = Special HsFunCon
    list_tycon_name       = Special HsListCon

    tuple_tycon_name :: Int -> HsQName
    tuple_tycon_name i    = tuple_con_name i

    unit_tycon, fun_tycon, list_tycon :: HsType
    unit_tycon	      = HsTyCon unit_tycon_name
    fun_tycon	      = HsTyCon fun_tycon_name
    list_tycon	      = HsTyCon list_tycon_name

    tuple_tycon :: Int -> HsType
    tuple_tycon i	      = HsTyCon (tuple_tycon_name i)