2 % (c) The AQUA Project, Glasgow University, 1996
4 \section[FieldLabel]{The @FieldLabel@ type}
7 #include "HsVersions.h"
9 module FieldLabel where
13 import Name ( Name{-instance Eq/Outputable-}, NamedThing(..), nameUnique )
14 import Type ( SYN_IE(Type) )
17 import Unique ( Uniquable(..) )
22 = FieldLabel Name -- Also used as the Name of the field selector Id
23 Type -- Type of the field; may have free type variables that
24 -- are the tyvar of the constructor
25 -- e.g. data T a = MkT { op1 :: a -> a, op2 :: a -> Int }
26 -- The type in the FieldLabel for op1 will be simply (a->a).
28 FieldLabelTag -- Indicates position within constructor
29 -- If the same field occurs in more than one constructor
30 -- then it'll have a separate FieldLabel on each occasion,
31 -- but with a single name (and presumably the same type!)
33 type FieldLabelTag = Int
35 mkFieldLabel = FieldLabel
37 firstFieldLabelTag :: FieldLabelTag
38 firstFieldLabelTag = 1
40 allFieldLabelTags :: [FieldLabelTag]
41 allFieldLabelTags = [1..]
43 fieldLabelName (FieldLabel n _ _) = n
44 fieldLabelType (FieldLabel _ ty _) = ty
45 fieldLabelTag (FieldLabel _ _ tag) = tag
47 instance Eq FieldLabel where
48 (FieldLabel n1 _ _) == (FieldLabel n2 _ _) = n1 == n2
50 instance Outputable FieldLabel where
51 ppr sty (FieldLabel n _ _) = ppr sty n
53 instance NamedThing FieldLabel where
54 getName (FieldLabel n _ _) = n
56 instance Uniquable FieldLabel where
57 uniqueOf (FieldLabel n _ _) = nameUnique n