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%
% (c) The AQUA Project, Glasgow University, 1996-1998
%
\section[FieldLabel]{The @FieldLabel@ type}
\begin{code}
module FieldLabel(
FieldLabel, -- Abstract
mkFieldLabel,
fieldLabelName, fieldLabelTyCon, fieldLabelType, fieldLabelTag,
FieldLabelTag,
firstFieldLabelTag, allFieldLabelTags
) where
#include "HsVersions.h"
import Type( Type )
import TyCon( TyCon )
import Name ( Name{-instance Eq/Outputable-}, NamedThing(..), nameUnique )
import Outputable
import Unique ( Uniquable(..) )
\end{code}
\begin{code}
data FieldLabel
= FieldLabel Name -- Also used as the Name of the field selector Id
TyCon -- Parent type constructor
Type -- Type of the field; may have free type variables that
-- are the tyvars of its parent *data* constructor, and
-- those will be the same as the tyvars of its parent *type* constructor
-- e.g. data T a = MkT { op1 :: a -> a, op2 :: a -> Int }
-- The type in the FieldLabel for op1 will be simply (a->a).
FieldLabelTag -- Indicates position within constructor
-- (starting with firstFieldLabelTag)
--
-- If the same field occurs in more than one constructor
-- then it'll have a separate FieldLabel on each occasion,
-- but with a single name (and presumably the same type!)
type FieldLabelTag = Int
mkFieldLabel = FieldLabel
firstFieldLabelTag :: FieldLabelTag
firstFieldLabelTag = 1
allFieldLabelTags :: [FieldLabelTag]
allFieldLabelTags = [firstFieldLabelTag..]
fieldLabelName (FieldLabel n _ _ _) = n
fieldLabelTyCon (FieldLabel _ tc _ _) = tc
fieldLabelType (FieldLabel _ _ ty _) = ty
fieldLabelTag (FieldLabel _ _ _ tag) = tag
instance Eq FieldLabel where
fl1 == fl2 = fieldLabelName fl1 == fieldLabelName fl2
instance Outputable FieldLabel where
ppr fl = ppr (fieldLabelName fl)
instance NamedThing FieldLabel where
getName = fieldLabelName
instance Uniquable FieldLabel where
getUnique fl = nameUnique (fieldLabelName fl)
\end{code}
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