2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[Class]{The @Class@ datatype}
8 Class, ClassOpItem, ClassPred, ClassContext, FunDep,
11 mkClass, classTyVars, classArity,
12 classKey, className, classSelIds, classTyCon,
13 classBigSig, classExtraBigSig, classTvsFds
16 #include "HsVersions.h"
18 import {-# SOURCE #-} TyCon ( TyCon )
19 import {-# SOURCE #-} TypeRep ( Type )
21 import Var ( Id, TyVar )
22 import Name ( NamedThing(..), Name )
23 import BasicTypes ( Arity )
24 import Unique ( Unique, Uniquable(..) )
29 %************************************************************************
31 \subsection[Class-basic]{@Class@: basic definition}
33 %************************************************************************
35 A @Class@ corresponds to a Greek kappa in the static semantics:
40 classKey :: Unique, -- Key for fast comparison
43 classTyVars :: [TyVar], -- The class type variables
44 classFunDeps :: [FunDep TyVar], -- The functional dependencies
46 classSCTheta :: [(Class,[Type])], -- Immediate superclasses, and the
47 classSCSels :: [Id], -- corresponding selector functions to
48 -- extract them from a dictionary of this
51 classOpStuff :: [ClassOpItem], -- Ordered by tag
53 classTyCon :: TyCon -- The data type constructor for dictionaries
56 type ClassPred = (Class, [Type])
57 type ClassContext = [ClassPred]
59 type FunDep a = ([a],[a]) -- e.g. class C a b c | a b -> c, a c -> b where ...
60 -- Here fun-deps are [([a,b],[c]), ([a,c],[b])]
62 type ClassOpItem = (Id, DefMeth Id)
63 -- Selector function; contains unfolding
64 -- Default-method info
66 data DefMeth id = NoDefMeth -- No default method
67 | DefMeth id -- A polymorphic default method (named id)
68 | GenDefMeth -- A generic default method
72 The @mkClass@ function fills in the indirect superclasses.
75 mkClass :: Name -> [TyVar]
76 -> [([TyVar], [TyVar])]
77 -> [(Class,[Type])] -> [Id]
82 mkClass name tyvars fds super_classes superdict_sels
84 = Class { classKey = getUnique name,
88 classSCTheta = super_classes,
89 classSCSels = superdict_sels,
90 classOpStuff = op_stuff,
94 %************************************************************************
96 \subsection[Class-selectors]{@Class@: simple selectors}
98 %************************************************************************
100 The rest of these functions are just simple selectors.
103 classArity :: Class -> Arity
104 classArity clas = length (classTyVars clas)
105 -- Could memoise this
107 classSelIds (Class {classSCSels = sc_sels, classOpStuff = op_stuff})
108 = sc_sels ++ [op_sel | (op_sel, _) <- op_stuff]
111 = (classTyVars c, classFunDeps c)
113 classBigSig (Class {classTyVars = tyvars, classSCTheta = sc_theta,
114 classSCSels = sc_sels, classOpStuff = op_stuff})
115 = (tyvars, sc_theta, sc_sels, op_stuff)
116 classExtraBigSig (Class {classTyVars = tyvars, classFunDeps = fundeps,
117 classSCTheta = sc_theta, classSCSels = sc_sels,
118 classOpStuff = op_stuff})
119 = (tyvars, fundeps, sc_theta, sc_sels, op_stuff)
123 %************************************************************************
125 \subsection[Class-instances]{Instance declarations for @Class@}
127 %************************************************************************
129 We compare @Classes@ by their keys (which include @Uniques@).
132 instance Eq Class where
133 c1 == c2 = classKey c1 == classKey c2
134 c1 /= c2 = classKey c1 /= classKey c2
136 instance Ord Class where
137 c1 <= c2 = classKey c1 <= classKey c2
138 c1 < c2 = classKey c1 < classKey c2
139 c1 >= c2 = classKey c1 >= classKey c2
140 c1 > c2 = classKey c1 > classKey c2
141 compare c1 c2 = classKey c1 `compare` classKey c2
145 instance Uniquable Class where
146 getUnique c = classKey c
148 instance NamedThing Class where
149 getName clas = className clas
151 instance Outputable Class where
152 ppr c = ppr (getName c)
154 instance Show Class where
155 showsPrec p c = showsPrecSDoc p (ppr c)