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(..) )
27 import Util ( notNull )
30 %************************************************************************
32 \subsection[Class-basic]{@Class@: basic definition}
34 %************************************************************************
36 A @Class@ corresponds to a Greek kappa in the static semantics:
41 classKey :: Unique, -- Key for fast comparison
44 classTyVars :: [TyVar], -- The class type variables
45 classFunDeps :: [FunDep TyVar], -- The functional dependencies
47 classSCTheta :: [PredType], -- Immediate superclasses, and the
48 classSCSels :: [Id], -- corresponding selector functions to
49 -- extract them from a dictionary of this
52 classOpStuff :: [ClassOpItem], -- Ordered by tag
54 classTyCon :: TyCon -- The data type constructor for dictionaries
57 type FunDep a = ([a],[a]) -- e.g. class C a b c | a b -> c, a c -> b where ...
58 -- Here fun-deps are [([a,b],[c]), ([a,c],[b])]
60 type ClassOpItem = (Id, DefMeth Name)
61 -- Selector function; contains unfolding
62 -- Default-method info
64 data DefMeth id = NoDefMeth -- No default method
65 | DefMeth id -- A polymorphic default method (named id)
66 | GenDefMeth -- A generic default method
70 The @mkClass@ function fills in the indirect superclasses.
73 mkClass :: Name -> [TyVar]
74 -> [([TyVar], [TyVar])]
80 mkClass name tyvars fds super_classes superdict_sels
82 = Class { classKey = getUnique name,
86 classSCTheta = super_classes,
87 classSCSels = superdict_sels,
88 classOpStuff = op_stuff,
92 %************************************************************************
94 \subsection[Class-selectors]{@Class@: simple selectors}
96 %************************************************************************
98 The rest of these functions are just simple selectors.
101 classArity :: Class -> Arity
102 classArity clas = length (classTyVars clas)
103 -- Could memoise this
105 classSelIds (Class {classSCSels = sc_sels, classOpStuff = op_stuff})
106 = sc_sels ++ [op_sel | (op_sel, _) <- op_stuff]
109 = (classTyVars c, classFunDeps c)
111 classBigSig (Class {classTyVars = tyvars, classSCTheta = sc_theta,
112 classSCSels = sc_sels, classOpStuff = op_stuff})
113 = (tyvars, sc_theta, sc_sels, op_stuff)
114 classExtraBigSig (Class {classTyVars = tyvars, classFunDeps = fundeps,
115 classSCTheta = sc_theta, classSCSels = sc_sels,
116 classOpStuff = op_stuff})
117 = (tyvars, fundeps, sc_theta, sc_sels, op_stuff)
119 classHasFDs :: Class -> Bool
120 classHasFDs (Class {classFunDeps = fundeps}) = notNull fundeps
124 %************************************************************************
126 \subsection[Class-instances]{Instance declarations for @Class@}
128 %************************************************************************
130 We compare @Classes@ by their keys (which include @Uniques@).
133 instance Eq Class where
134 c1 == c2 = classKey c1 == classKey c2
135 c1 /= c2 = classKey c1 /= classKey c2
137 instance Ord Class where
138 c1 <= c2 = classKey c1 <= classKey c2
139 c1 < c2 = classKey c1 < classKey c2
140 c1 >= c2 = classKey c1 >= classKey c2
141 c1 > c2 = classKey c1 > classKey c2
142 compare c1 c2 = classKey c1 `compare` classKey c2
146 instance Uniquable Class where
147 getUnique c = classKey c
149 instance NamedThing Class where
150 getName clas = className clas
152 instance Outputable Class where
153 ppr c = ppr (getName c)
155 instance Show Class where
156 showsPrec p c = showsPrecSDoc p (ppr c)