--- /dev/null
+{-# OPTIONS -Wall -fno-warn-name-shadowing #-}
+{-
+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 Language.Core.Prep where
+
+import Data.Either
+import Data.List
+
+import Language.Core.Prims
+import Language.Core.Core
+import Language.Core.Env
+import Language.Core.Check
+
+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((Nothing,x),t,e))) =
+ (eextend venv (x,t), Nonrec(Vdef((Nothing,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((Nothing,x),t,_) <- vdefs]
+
+ prepExp _ (Var qv) = Var qv
+ prepExp _ (Dcon qdc) = Dcon qdc
+ prepExp _ (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((Nothing,x),t,b))) e)
+ | (kindOfTy tvenv t `eqKind` Kunlifted && suspends b) =
+ -- There are two places where we call the typechecker, one of them
+ -- here.
+ -- We need to know the type of the let body in order to construct
+ -- a case expression.
+ -- need to extend the env with the let-bound var too!
+ let eTy = typeOfExp (eextend venv (x, t), tvenv) e in
+ Case (prepExp env b) (x,t)
+ eTy
+ [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 t alts) = Case (prepExp env e) vb t (map (prepAlt (eextend venv vb,tvenv)) alts)
+ prepExp env (Cast e t) = Cast (prepExp env e) t
+ prepExp env (Note s e) = Note s (prepExp env e)
+ prepExp _ (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 =
+ -- possibly dubious to assume no type args
+ 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(qv@(_,p)))) as | isPrimVar qv =
+ etaExpand (snd (unzip extraTbs)) (drop n atys) (rewindApp env op as)
+ where -- TODO: avoid copying code. these two cases are the same
+
+ -- etaExpand needs to add the type arguments too! Bah!
+ (tbs, atys0, _) = (maybe (error "unwindApp") splitTy (elookup (venv_ primEnv) p))
+ n_args = length ts
+ (appliedTbs, extraTbs) = (take n_args tbs, drop n_args tbs)
+ atys = map (substl (map fst appliedTbs) ts) atys0
+ ts = [t | Right t <- as]
+ n = length [e | Left e <- as]
+ unwindApp env op as = rewindApp env op as
+
+
+ etaExpand :: [Kind] -> [Ty] -> Exp -> Exp
+ etaExpand ks ts e =
+ -- what a pain
+ let tyArgs = [("$t_"++(show i),k) | (i, k) <- zip [(1::Integer)..] ks]
+ termArgs = [ ('$':(show i),t) | (i,t) <- zip [(1::Integer)..] ts] in
+ foldr (\ (t1,k1) e -> Lam (Tb (t1,k1)) e)
+ (foldr (\ (v,t) e -> Lam (Vb (v,t)) e)
+ (foldl (\ e (v,_) -> App e (Var (unqual v)))
+ (foldl (\ e (tv,_) -> Appt e (Tvar tv))
+ e tyArgs)
+ termArgs) termArgs)
+ tyArgs
+
+ rewindApp _ e [] = e
+ rewindApp env@(venv,tvenv) e1 (Left e2:as) | kindOfTy tvenv t `eqKind` Kunlifted && suspends e2 =
+ -- This is the other place where we call the typechecker.
+ Case newScrut (v,t) (typeOfExp env' rhs) [Adefault rhs]
+ where newScrut = prepExp env e2
+ rhs = (rewindApp env' (App e1 (Var (unqual v))) as)
+ -- note:
+ -- e1 gets moved inside rhs. so if we pick a case
+ -- var name (outside e1) equal to a name bound *inside*
+ -- e1, the binding *inside* e1 will shadow "v"
+ -- Which would be name capture!
+ -- So, we pass the bound vars of e1 to freshVar along with
+ -- the domain of the current env.
+ v = freshVar (edomain venv `union` (boundVars e1))
+ 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 vs = maximum ("":vs) ++ "x" -- one simple way!
+
+ typeOfExp :: (Venv, Tvenv) -> Exp -> Ty
+ typeOfExp = uncurry (checkExpr mn globalEnv tdefs)
+
+ kindOfTy :: Tvenv -> Ty -> Kind
+ kindOfTy tvenv = checkType mn globalEnv tdefs tvenv
+
+ {- Return false for those expressions for which Interp.suspendExp builds a thunk. -}
+ suspends (Var _) = False
+ suspends (Lit _) = False
+ suspends (Lam (Vb _) _) = False
+ suspends (Lam _ e) = suspends e
+ suspends (Appt e _) = suspends e
+ suspends (Cast e _) = suspends e
+ suspends (Note _ e) = suspends e
+ suspends (External _ _) = False
+ suspends _ = True
+
+ mlookup :: (Envs -> Env a b) -> Env a b -> Mname -> Env a b
+ mlookup _ local_env Nothing = local_env
+ mlookup selector _ (Just m) =
+ case elookup globalEnv m of
+ Just env -> selector env
+ Nothing -> error ("Prep: undefined module name: " ++ show 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)
+
+boundVars :: Exp -> [Id]
+boundVars (Lam (Vb (v,_)) e) = [v] `union` boundVars e
+boundVars (Lam _ e) = boundVars e
+boundVars (Let vds e) = (boundVarsVdefs vds) `union` boundVars e
+boundVars (Case scrut (v,_) _ alts) =
+ [v] `union` (boundVars scrut) `union` boundVarsAlts alts
+boundVars (Cast e _) = boundVars e
+boundVars (Note _ e) = boundVars e
+boundVars (App e1 e2) = boundVars e1 `union` boundVars e2
+boundVars (Appt e _) = boundVars e
+boundVars _ = []
+
+boundVarsVdefs :: Vdefg -> [Id]
+boundVarsVdefs (Rec vds) = nub (concatMap boundVarsVdef vds)
+boundVarsVdefs (Nonrec vd) = boundVarsVdef vd
+
+boundVarsVdef :: Vdef -> [Id]
+boundVarsVdef (Vdef ((_,v),_,e)) = [v] `union` boundVars e
+
+boundVarsAlts :: [Alt] -> [Var]
+boundVarsAlts as = nub (concatMap boundVarsAlt as)
+
+boundVarsAlt :: Alt -> [Var]
+boundVarsAlt (Acon _ _ vbs e) = (map fst vbs) `union` (boundVars e)
+boundVarsAlt (Alit _ e) = boundVars e
+boundVarsAlt (Adefault e) = boundVars e
\ No newline at end of file
projects / ghc-hetmet.git / blobdiff