--- /dev/null
+{-
+Preprocess a module to normalize it in the following ways:
+ (1) Saturate all constructor and primop applications.
+ (2) Arrange that any non-trivial expression of unlifted kind ('#')
+ is turned into the scrutinee of a Case.
+After these preprocessing steps, Core can be interpreted (or given an operational semantics)
+ ignoring type information almost completely.
+-}
+
+
+module Prep where
+
+import Prims
+import Core
+import Printer
+import Env
+import Check
+
+primArgTys :: Env Var [Ty]
+primArgTys = efromlist (map f Prims.primVals)
+ where f (v,t) = (v,atys)
+ where (_,atys,_) = splitTy t
+
+prepModule :: Menv -> Module -> Module
+prepModule globalEnv (Module mn tdefs vdefgs) =
+ Module mn tdefs vdefgs'
+ where
+ (_,vdefgs') = foldl prepTopVdefg (eempty,[]) vdefgs
+
+ prepTopVdefg (venv,vdefgs) vdefg = (venv',vdefgs ++ [vdefg'])
+ where (venv',vdefg') = prepVdefg (venv,eempty) vdefg
+
+ prepVdefg (env@(venv,_)) (Nonrec(Vdef(("",x),t,e))) =
+ (eextend venv (x,t), Nonrec(Vdef(("",x),t,prepExp env e)))
+ prepVdefg (env@(venv,_)) (Nonrec(Vdef(qx,t,e))) =
+ (venv, Nonrec(Vdef(qx,t,prepExp env e)))
+ prepVdefg (venv,tvenv) (Rec vdefs) =
+ (venv',Rec [Vdef(qx,t,prepExp (venv',tvenv) e) | Vdef(qx,t,e) <- vdefs])
+ where venv' = foldl eextend venv [(x,t) | Vdef(("",x),t,_) <- vdefs]
+
+ prepExp env (Var qv) = Var qv
+ prepExp env (Dcon qdc) = Dcon qdc
+ prepExp env (Lit l) = Lit l
+ prepExp env e@(App _ _) = unwindApp env e []
+ prepExp env e@(Appt _ _) = unwindApp env e []
+ prepExp (venv,tvenv) (Lam (Vb vb) e) = Lam (Vb vb) (prepExp (eextend venv vb,tvenv) e)
+ prepExp (venv,tvenv) (Lam (Tb tb) e) = Lam (Tb tb) (prepExp (venv,eextend tvenv tb) e)
+ prepExp env@(venv,tvenv) (Let (Nonrec(Vdef(("",x),t,b))) e) | kindof tvenv t == Kunlifted && suspends b =
+ Case (prepExp env b) (x,t) [Adefault (prepExp (eextend venv (x,t),tvenv) e)]
+ prepExp (venv,tvenv) (Let vdefg e) = Let vdefg' (prepExp (venv',tvenv) e)
+ where (venv',vdefg') = prepVdefg (venv,tvenv) vdefg
+ prepExp env@(venv,tvenv) (Case e vb alts) = Case (prepExp env e) vb (map (prepAlt (eextend venv vb,tvenv)) alts)
+ prepExp env (Coerce t e) = Coerce t (prepExp env e)
+ prepExp env (Note s e) = Note s (prepExp env e)
+ prepExp env (External s t) = External s t
+
+ prepAlt (venv,tvenv) (Acon qdc tbs vbs e) = Acon qdc tbs vbs (prepExp (foldl eextend venv vbs,foldl eextend tvenv tbs) e)
+ prepAlt env (Alit l e) = Alit l (prepExp env e)
+ prepAlt env (Adefault e) = Adefault (prepExp env e)
+
+
+ unwindApp env (App e1 e2) as = unwindApp env e1 (Left e2:as)
+ unwindApp env (Appt e t) as = unwindApp env e (Right t:as)
+ unwindApp env (op@(Dcon qdc)) as =
+ etaExpand (drop n atys) (rewindApp env op as)
+ where (tbs,atys0,_) = splitTy (qlookup cenv_ eempty qdc)
+ atys = map (substl (map fst tbs) ts) atys0
+ ts = [t | Right t <- as]
+ n = length [e | Left e <- as]
+ unwindApp env (op@(Var(m,p))) as | m == primMname =
+ etaExpand (drop n atys) (rewindApp env op as)
+ where Just atys = elookup primArgTys p
+ n = length [e | Left e <- as]
+ unwindApp env op as = rewindApp env op as
+
+
+ etaExpand ts e = foldl g e [('$':(show i),t) | (i,t) <- zip [1..] ts]
+ where g e (v,t) = Lam (Vb(v,t)) (App e (Var ("",v)))
+
+ rewindApp env e [] = e
+ rewindApp env@(venv,tvenv) e1 (Left e2:as) | kindof tvenv t == Kunlifted && suspends e2 =
+ Case (prepExp env' e2) (v,t)
+ [Adefault (rewindApp env' (App e1 (Var ("",v))) as)]
+ where v = freshVar venv
+ t = typeofExp env e2
+ env' = (eextend venv (v,t),tvenv)
+ rewindApp env e1 (Left e2:as) = rewindApp env (App e1 (prepExp env e2)) as
+ rewindApp env e (Right t:as) = rewindApp env (Appt e t) as
+
+ freshVar venv = maximum ("":edomain venv) ++ "x" -- one simple way!
+
+ typeofExp :: (Venv,Tvenv) -> Exp -> Ty
+ typeofExp (venv,_) (Var qv) = qlookup venv_ venv qv
+ typeofExp env (Dcon qdc) = qlookup cenv_ eempty qdc
+ typeofExp env (Lit l) = typeofLit l
+ where typeofLit (Lint _ t) = t
+ typeofLit (Lrational _ t) = t
+ typeofLit (Lchar _ t) = t
+ typeofLit (Lstring _ t) = t
+ typeofExp env (App e1 e2) = t
+ where (Tapp(Tapp _ t0) t) = typeofExp env e1
+ typeofExp env (Appt e t) = substl [tv] [t] t'
+ where (Tforall (tv,_) t') = typeofExp env e
+ typeofExp (venv,tvenv) (Lam (Vb(v,t)) e) = tArrow t (typeofExp (eextend venv (v,t),tvenv) e)
+ typeofExp (venv,tvenv) (Lam (Tb tb) e) = Tforall tb (typeofExp (venv,eextend tvenv tb) e)
+ typeofExp (venv,tvenv) (Let vdefg e) = typeofExp (venv',tvenv) e
+ where venv' = case vdefg of
+ Nonrec (Vdef((_,x),t,_)) -> eextend venv (x,t)
+ Rec vdefs -> foldl eextend venv [(x,t) | Vdef((_,x),t,_) <- vdefs]
+ typeofExp (venv,tvenv) (Case _ vb (alt:_)) = typeofAlt (eextend venv vb,tvenv) alt
+ where typeofAlt (venv,tvenv) (Acon _ tbs vbs e) = typeofExp (foldl eextend venv vbs,foldl eextend tvenv tbs) e
+ typeofAlt env (Alit _ e) = typeofExp env e
+ typeofAlt env (Adefault e) = typeofExp env e
+ typeofExp env (Coerce t _) = t
+ typeofExp env (Note _ e) = typeofExp env e
+ typeofExp env (External _ t) = t
+
+ {- Return false for those expressions for which Interp.suspendExp buidds a thunk. -}
+ suspends (Var _) = False
+ suspends (Lit _) = False
+ suspends (Lam (Vb _) _) = False
+ suspends (Lam _ e) = suspends e
+ suspends (Appt e _) = suspends e
+ suspends (Coerce _ e) = suspends e
+ suspends (Note _ e) = suspends e
+ suspends (External _ _) = False
+ suspends _ = True
+
+ kindof :: Tvenv -> Ty -> Kind
+ kindof tvenv (Tvar tv) =
+ case elookup tvenv tv of
+ Just k -> k
+ Nothing -> error ("impossible Tyvar " ++ show tv)
+ kindof tvenv (Tcon qtc) = qlookup tcenv_ eempty qtc
+ kindof tvenv (Tapp t1 t2) = k2
+ where Karrow _ k2 = kindof tvenv t1
+ kindof tvenv (Tforall _ t) = kindof tvenv t
+
+ mlookup :: (Envs -> Env a b) -> Env a b -> Mname -> Env a b
+ mlookup _ local_env "" = local_env
+ mlookup selector _ m =
+ case elookup globalEnv m of
+ Just env -> selector env
+ Nothing -> error ("undefined module name: " ++ m)
+
+ qlookup :: (Ord a, Show a) => (Envs -> Env a b) -> Env a b -> (Mname,a) -> b
+ qlookup selector local_env (m,k) =
+ case elookup (mlookup selector local_env m) k of
+ Just v -> v
+ Nothing -> error ("undefined identifier: " ++ show k)
+
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