2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[Class]{The @Class@ datatype}
8 Class, ClassOpItem, FunDep,
11 mkClass, classTyVars, classArity,
12 classKey, className, classSelIds, classTyCon,
13 classBigSig, classExtraBigSig, classTvsFds, classSCTheta,
17 #include "HsVersions.h"
19 import {-# SOURCE #-} TyCon ( TyCon )
20 import {-# SOURCE #-} TypeRep ( PredType )
22 import Var ( Id, TyVar )
23 import Name ( NamedThing(..), Name )
24 import BasicTypes ( Arity )
25 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 :: [PredType], -- 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 FunDep a = ([a],[a]) -- e.g. class C a b c | a b -> c, a c -> b where ...
57 -- Here fun-deps are [([a,b],[c]), ([a,c],[b])]
59 type ClassOpItem = (Id, DefMeth Name)
60 -- Selector function; contains unfolding
61 -- Default-method info
63 data DefMeth id = NoDefMeth -- No default method
64 | DefMeth id -- A polymorphic default method (named id)
65 | GenDefMeth -- A generic default method
69 The @mkClass@ function fills in the indirect superclasses.
72 mkClass :: Name -> [TyVar]
73 -> [([TyVar], [TyVar])]
79 mkClass name tyvars fds super_classes superdict_sels
81 = Class { classKey = getUnique name,
85 classSCTheta = super_classes,
86 classSCSels = superdict_sels,
87 classOpStuff = op_stuff,
91 %************************************************************************
93 \subsection[Class-selectors]{@Class@: simple selectors}
95 %************************************************************************
97 The rest of these functions are just simple selectors.
100 classArity :: Class -> Arity
101 classArity clas = length (classTyVars clas)
102 -- Could memoise this
104 classSelIds (Class {classSCSels = sc_sels, classOpStuff = op_stuff})
105 = sc_sels ++ [op_sel | (op_sel, _) <- op_stuff]
108 = (classTyVars c, classFunDeps c)
110 classBigSig (Class {classTyVars = tyvars, classSCTheta = sc_theta,
111 classSCSels = sc_sels, classOpStuff = op_stuff})
112 = (tyvars, sc_theta, sc_sels, op_stuff)
113 classExtraBigSig (Class {classTyVars = tyvars, classFunDeps = fundeps,
114 classSCTheta = sc_theta, classSCSels = sc_sels,
115 classOpStuff = op_stuff})
116 = (tyvars, fundeps, sc_theta, sc_sels, op_stuff)
118 classHasFDs :: Class -> Bool
119 classHasFDs (Class {classFunDeps = fundeps}) = not (null fundeps)
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)