2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[Class]{The @Class@ datatype}
8 Class, ClassOpItem, ClassPred, ClassContext, FunDep,
10 mkClass, classTyVars, classArity,
11 classKey, className, classSelIds, classTyCon,
12 classBigSig, classExtraBigSig, classTvsFds
15 #include "HsVersions.h"
17 import {-# SOURCE #-} TyCon ( TyCon )
18 import {-# SOURCE #-} TypeRep ( Type )
20 import Var ( Id, TyVar )
21 import Name ( NamedThing(..), Name )
22 import BasicTypes ( Arity )
23 import Unique ( Unique, Uniquable(..) )
28 %************************************************************************
30 \subsection[Class-basic]{@Class@: basic definition}
32 %************************************************************************
34 A @Class@ corresponds to a Greek kappa in the static semantics:
39 classKey :: Unique, -- Key for fast comparison
42 classTyVars :: [TyVar], -- The class type variables
43 classFunDeps :: [FunDep TyVar], -- The functional dependencies
45 classSCTheta :: [(Class,[Type])], -- Immediate superclasses, and the
46 classSCSels :: [Id], -- corresponding selector functions to
47 -- extract them from a dictionary of this
50 classOpStuff :: [ClassOpItem], -- Ordered by tag
52 classTyCon :: TyCon -- The data type constructor for dictionaries
55 type ClassPred = (Class, [Type])
56 type ClassContext = [ClassPred]
58 type FunDep a = ([a],[a]) -- e.g. class C a b c | a b -> c, a c -> b where ...
59 -- Here fun-deps are [([a,b],[c]), ([a,c],[b])]
61 type ClassOpItem = (Id, -- Selector function; contains unfolding
62 Id, -- Default methods
63 Bool) -- True <=> an explicit default method was
64 -- supplied in the class decl
67 The @mkClass@ function fills in the indirect superclasses.
70 mkClass :: Name -> [TyVar]
71 -> [([TyVar], [TyVar])]
72 -> [(Class,[Type])] -> [Id]
77 mkClass name tyvars fds super_classes superdict_sels
79 = Class { classKey = getUnique name,
83 classSCTheta = super_classes,
84 classSCSels = superdict_sels,
85 classOpStuff = op_stuff,
89 %************************************************************************
91 \subsection[Class-selectors]{@Class@: simple selectors}
93 %************************************************************************
95 The rest of these functions are just simple selectors.
98 classArity :: Class -> Arity
99 classArity clas = length (classTyVars clas)
100 -- Could memoise this
102 classSelIds (Class {classSCSels = sc_sels, classOpStuff = op_stuff})
103 = sc_sels ++ [op_sel | (op_sel, _, _) <- op_stuff]
106 = (classTyVars c, classFunDeps c)
108 classBigSig (Class {classTyVars = tyvars, classSCTheta = sc_theta,
109 classSCSels = sc_sels, classOpStuff = op_stuff})
110 = (tyvars, sc_theta, sc_sels, op_stuff)
111 classExtraBigSig (Class {classTyVars = tyvars, classFunDeps = fundeps,
112 classSCTheta = sc_theta, classSCSels = sc_sels,
113 classOpStuff = op_stuff})
114 = (tyvars, fundeps, sc_theta, sc_sels, op_stuff)
118 %************************************************************************
120 \subsection[Class-instances]{Instance declarations for @Class@}
122 %************************************************************************
124 We compare @Classes@ by their keys (which include @Uniques@).
127 instance Eq Class where
128 c1 == c2 = classKey c1 == classKey c2
129 c1 /= c2 = classKey c1 /= classKey c2
131 instance Ord Class where
132 c1 <= c2 = classKey c1 <= classKey c2
133 c1 < c2 = classKey c1 < classKey c2
134 c1 >= c2 = classKey c1 >= classKey c2
135 c1 > c2 = classKey c1 > classKey c2
136 compare c1 c2 = classKey c1 `compare` classKey c2
140 instance Uniquable Class where
141 getUnique c = classKey c
143 instance NamedThing Class where
144 getName clas = className clas
146 instance Outputable Class where
147 ppr c = ppr (getName c)
149 instance Show Class where
150 showsPrec p c = showsPrecSDoc p (ppr c)