2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[Class]{The @Class@ datatype}
8 Class, ClassOpItem, ClassPred, ClassContext, FunDep,
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 Unique ( Unique, Uniquable(..) )
27 %************************************************************************
29 \subsection[Class-basic]{@Class@: basic definition}
31 %************************************************************************
33 A @Class@ corresponds to a Greek kappa in the static semantics:
38 classKey :: Unique, -- Key for fast comparison
41 classTyVars :: [TyVar], -- The class type variables
42 classFunDeps :: [FunDep TyVar], -- The functional dependencies
44 classSCTheta :: [(Class,[Type])], -- Immediate superclasses, and the
45 classSCSels :: [Id], -- corresponding selector functions to
46 -- extract them from a dictionary of this
49 classOpStuff :: [ClassOpItem], -- Ordered by tag
51 classTyCon :: TyCon -- The data type constructor for dictionaries
54 type ClassPred = (Class, [Type])
55 type ClassContext = [ClassPred]
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, -- Selector function; contains unfolding
61 Id, -- Default methods
62 Bool) -- True <=> an explicit default method was
63 -- supplied in the class decl
66 The @mkClass@ function fills in the indirect superclasses.
69 mkClass :: Name -> [TyVar]
70 -> [([TyVar], [TyVar])]
71 -> [(Class,[Type])] -> [Id]
76 mkClass name tyvars fds super_classes superdict_sels
78 = Class { classKey = getUnique name,
82 classSCTheta = super_classes,
83 classSCSels = superdict_sels,
84 classOpStuff = op_stuff,
88 %************************************************************************
90 \subsection[Class-selectors]{@Class@: simple selectors}
92 %************************************************************************
94 The rest of these functions are just simple selectors.
97 classSelIds (Class {classSCSels = sc_sels, classOpStuff = op_stuff})
98 = sc_sels ++ [op_sel | (op_sel, _, _) <- op_stuff]
101 = (classTyVars c, classFunDeps c)
103 classBigSig (Class {classTyVars = tyvars, classSCTheta = sc_theta,
104 classSCSels = sc_sels, classOpStuff = op_stuff})
105 = (tyvars, sc_theta, sc_sels, op_stuff)
106 classExtraBigSig (Class {classTyVars = tyvars, classFunDeps = fundeps,
107 classSCTheta = sc_theta, classSCSels = sc_sels,
108 classOpStuff = op_stuff})
109 = (tyvars, fundeps, sc_theta, sc_sels, op_stuff)
113 %************************************************************************
115 \subsection[Class-instances]{Instance declarations for @Class@}
117 %************************************************************************
119 We compare @Classes@ by their keys (which include @Uniques@).
122 instance Eq Class where
123 c1 == c2 = classKey c1 == classKey c2
124 c1 /= c2 = classKey c1 /= classKey c2
126 instance Ord Class where
127 c1 <= c2 = classKey c1 <= classKey c2
128 c1 < c2 = classKey c1 < classKey c2
129 c1 >= c2 = classKey c1 >= classKey c2
130 c1 > c2 = classKey c1 > classKey c2
131 compare c1 c2 = classKey c1 `compare` classKey c2
135 instance Uniquable Class where
136 getUnique c = classKey c
138 instance NamedThing Class where
139 getName clas = className clas
141 instance Outputable Class where
142 ppr c = ppr (getName c)
144 instance Show Class where
145 showsPrec p c = showsPrecSDoc p (ppr c)