1 {-# OPTIONS -Wall -fno-warn-name-shadowing #-}
3 Preprocess a module to normalize it in the following ways:
4 (1) Saturate all constructor and primop applications.
5 (2) Arrange that any non-trivial expression of unlifted kind ('#')
6 is turned into the scrutinee of a Case.
7 After these preprocessing steps, Core can be interpreted (or given an operational semantics)
8 ignoring type information almost completely.
12 module Language.Core.Prep where
17 import Language.Core.Prims
18 import Language.Core.Core
19 import Language.Core.Env
20 import Language.Core.Check
22 prepModule :: Menv -> Module -> Module
23 prepModule globalEnv (Module mn tdefs vdefgs) =
24 Module mn tdefs vdefgs'
27 (_,vdefgs') = foldl prepTopVdefg (eempty,[]) vdefgs
29 prepTopVdefg (venv,vdefgs) vdefg = (venv',vdefgs ++ [vdefg'])
30 where (venv',vdefg') = prepVdefg (venv,eempty) vdefg
32 prepVdefg (env@(venv,_)) (Nonrec(Vdef((Nothing,x),t,e))) =
33 (eextend venv (x,t), Nonrec(Vdef((Nothing,x),t,prepExp env e)))
34 prepVdefg (env@(venv,_)) (Nonrec(Vdef(qx,t,e))) =
35 (venv, Nonrec(Vdef(qx,t,prepExp env e)))
36 prepVdefg (venv,tvenv) (Rec vdefs) =
37 (venv',Rec [ Vdef(qx,t,prepExp (venv',tvenv) e) | Vdef(qx,t,e) <- vdefs])
38 where venv' = foldl eextend venv [(x,t) | Vdef((Nothing,x),t,_) <- vdefs]
40 prepExp _ (Var qv) = Var qv
41 prepExp _ (Dcon qdc) = Dcon qdc
42 prepExp _ (Lit l) = Lit l
43 prepExp env e@(App _ _) = unwindApp env e []
44 prepExp env e@(Appt _ _) = unwindApp env e []
45 prepExp (venv,tvenv) (Lam (Vb vb) e) = Lam (Vb vb) (prepExp (eextend venv vb,tvenv) e)
46 prepExp (venv,tvenv) (Lam (Tb tb) e) = Lam (Tb tb) (prepExp (venv,eextend tvenv tb) e)
47 prepExp env@(venv,tvenv) (Let (Nonrec(Vdef((Nothing,x),t,b))) e)
48 | (kindOfTy tvenv t `eqKind` Kunlifted && suspends b) =
49 -- There are two places where we call the typechecker, one of them
51 -- We need to know the type of the let body in order to construct
53 -- need to extend the env with the let-bound var too!
54 let eTy = typeOfExp (eextend venv (x, t), tvenv) e in
55 Case (prepExp env b) (x,t)
57 [Adefault (prepExp (eextend venv (x,t),tvenv) e)]
58 prepExp (venv,tvenv) (Let vdefg e) = Let vdefg' (prepExp (venv',tvenv) e)
59 where (venv',vdefg') = prepVdefg (venv,tvenv) vdefg
60 prepExp env@(venv,tvenv) (Case e vb t alts) = Case (prepExp env e) vb t (map (prepAlt (eextend venv vb,tvenv)) alts)
61 prepExp env (Cast e t) = Cast (prepExp env e) t
62 prepExp env (Note s e) = Note s (prepExp env e)
63 prepExp _ (External s t) = External s t
65 prepAlt (venv,tvenv) (Acon qdc tbs vbs e) = Acon qdc tbs vbs (prepExp (foldl eextend venv vbs,foldl eextend tvenv tbs) e)
66 prepAlt env (Alit l e) = Alit l (prepExp env e)
67 prepAlt env (Adefault e) = Adefault (prepExp env e)
70 unwindApp env (App e1 e2) as = unwindApp env e1 (Left e2:as)
71 unwindApp env (Appt e t) as = unwindApp env e (Right t:as)
72 unwindApp env (op@(Dcon qdc)) as =
73 -- possibly dubious to assume no type args
74 etaExpand [] (drop n atys) (rewindApp env op as)
75 where (tbs,atys0,_) = splitTy (qlookup cenv_ eempty qdc)
76 atys = map (substl (map fst tbs) ts) atys0
77 ts = [t | Right t <- as]
78 n = length [e | Left e <- as]
79 unwindApp env (op@(Var(qv@(_,p)))) as | isPrimVar qv =
80 etaExpand (snd (unzip extraTbs)) (drop n atys) (rewindApp env op as)
81 where -- TODO: avoid copying code. these two cases are the same
83 -- etaExpand needs to add the type arguments too! Bah!
84 (tbs, atys0, _) = (maybe (error "unwindApp") splitTy (elookup (venv_ primEnv) p))
86 (appliedTbs, extraTbs) = (take n_args tbs, drop n_args tbs)
87 atys = map (substl (map fst appliedTbs) ts) atys0
88 ts = [t | Right t <- as]
89 n = length [e | Left e <- as]
90 unwindApp env op as = rewindApp env op as
93 etaExpand :: [Kind] -> [Ty] -> Exp -> Exp
96 let tyArgs = [("$t_"++(show i),k) | (i, k) <- zip [(1::Integer)..] ks]
97 termArgs = [ ('$':(show i),t) | (i,t) <- zip [(1::Integer)..] ts] in
98 foldr (\ (t1,k1) e -> Lam (Tb (t1,k1)) e)
99 (foldr (\ (v,t) e -> Lam (Vb (v,t)) e)
100 (foldl (\ e (v,_) -> App e (Var (unqual v)))
101 (foldl (\ e (tv,_) -> Appt e (Tvar tv))
107 rewindApp env@(venv,tvenv) e1 (Left e2:as) | kindOfTy tvenv t `eqKind` Kunlifted && suspends e2 =
108 -- This is the other place where we call the typechecker.
109 Case newScrut (v,t) (typeOfExp env' rhs) [Adefault rhs]
110 where newScrut = prepExp env e2
111 rhs = (rewindApp env' (App e1 (Var (unqual v))) as)
113 -- e1 gets moved inside rhs. so if we pick a case
114 -- var name (outside e1) equal to a name bound *inside*
115 -- e1, the binding *inside* e1 will shadow "v"
116 -- Which would be name capture!
117 -- So, we pass the bound vars of e1 to freshVar along with
118 -- the domain of the current env.
119 v = freshVar (edomain venv `union` (boundVars e1))
121 env' = (eextend venv (v,t),tvenv)
122 rewindApp env e1 (Left e2:as) = rewindApp env (App e1 (prepExp env e2)) as
123 rewindApp env e (Right t:as) = rewindApp env (Appt e t) as
125 freshVar vs = maximum ("":vs) ++ "x" -- one simple way!
127 typeOfExp :: (Venv, Tvenv) -> Exp -> Ty
128 typeOfExp = uncurry (checkExpr mn globalEnv tdefs)
130 kindOfTy :: Tvenv -> Ty -> Kind
131 kindOfTy tvenv = checkType mn globalEnv tdefs tvenv
133 {- Return false for those expressions for which Interp.suspendExp builds a thunk. -}
134 suspends (Var _) = False
135 suspends (Lit _) = False
136 suspends (Lam (Vb _) _) = False
137 suspends (Lam _ e) = suspends e
138 suspends (Appt e _) = suspends e
139 suspends (Cast e _) = suspends e
140 suspends (Note _ e) = suspends e
141 suspends (External _ _) = False
144 mlookup :: (Envs -> Env a b) -> Env a b -> Mname -> Env a b
145 mlookup _ local_env Nothing = local_env
146 mlookup selector _ (Just m) =
147 case elookup globalEnv m of
148 Just env -> selector env
149 Nothing -> error ("Prep: undefined module name: " ++ show m)
151 qlookup :: (Ord a, Show a) => (Envs -> Env a b) -> Env a b -> (Mname,a) -> b
152 qlookup selector local_env (m,k) =
153 case elookup (mlookup selector local_env m) k of
155 Nothing -> error ("undefined identifier: " ++ show k)
157 boundVars :: Exp -> [Id]
158 boundVars (Lam (Vb (v,_)) e) = [v] `union` boundVars e
159 boundVars (Lam _ e) = boundVars e
160 boundVars (Let vds e) = (boundVarsVdefs vds) `union` boundVars e
161 boundVars (Case scrut (v,_) _ alts) =
162 [v] `union` (boundVars scrut) `union` boundVarsAlts alts
163 boundVars (Cast e _) = boundVars e
164 boundVars (Note _ e) = boundVars e
165 boundVars (App e1 e2) = boundVars e1 `union` boundVars e2
166 boundVars (Appt e _) = boundVars e
169 boundVarsVdefs :: Vdefg -> [Id]
170 boundVarsVdefs (Rec vds) = nub (concatMap boundVarsVdef vds)
171 boundVarsVdefs (Nonrec vd) = boundVarsVdef vd
173 boundVarsVdef :: Vdef -> [Id]
174 boundVarsVdef (Vdef ((_,v),_,e)) = [v] `union` boundVars e
176 boundVarsAlts :: [Alt] -> [Var]
177 boundVarsAlts as = nub (concatMap boundVarsAlt as)
179 boundVarsAlt :: Alt -> [Var]
180 boundVarsAlt (Acon _ _ vbs e) = (map fst vbs) `union` (boundVars e)
181 boundVarsAlt (Alit _ e) = boundVars e
182 boundVarsAlt (Adefault e) = boundVars e