X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsListComp.lhs;h=1ecab67e10fbc580e8e79d854152c004db1b2b8d;hp=7fa78487e92d432bc8f4ce31ff2d512ce02b151c;hb=4ac2bb39dffb4b825ece73b349ff0d56d79092d7;hpb=5ccf658872ea2304f34eda6b1fb840fc1bfc0ba0 diff --git a/compiler/deSugar/DsListComp.lhs b/compiler/deSugar/DsListComp.lhs index 7fa7848..1ecab67 100644 --- a/compiler/deSugar/DsListComp.lhs +++ b/compiler/deSugar/DsListComp.lhs @@ -49,12 +49,12 @@ There will be at least one ``qualifier'' in the input. \begin{code} dsListComp :: [LStmt Id] - -> LHsExpr Id - -> Type -- Type of list elements + -> Type -- Type of entire list -> DsM CoreExpr -dsListComp lquals body elt_ty = do +dsListComp lquals res_ty = do dflags <- getDOptsDs let quals = map unLoc lquals + [elt_ty] = tcTyConAppArgs res_ty if not (dopt Opt_EnableRewriteRules dflags) || dopt Opt_IgnoreInterfacePragmas dflags -- Either rules are switched off, or we are ignoring what there are; @@ -62,8 +62,8 @@ dsListComp lquals body elt_ty = do -- Wadler-style desugaring || isParallelComp quals -- Foldr-style desugaring can't handle parallel list comprehensions - then deListComp quals body (mkNilExpr elt_ty) - else mkBuildExpr elt_ty (\(c, _) (n, _) -> dfListComp c n quals body) + then deListComp quals (mkNilExpr elt_ty) + else mkBuildExpr elt_ty (\(c, _) (n, _) -> dfListComp c n quals) -- Foldr/build should be enabled, so desugar -- into foldrs and builds @@ -83,12 +83,11 @@ dsListComp lquals body elt_ty = do -- and the type of the elements that it outputs (tuples of binders) dsInnerListComp :: ([LStmt Id], [Id]) -> DsM (CoreExpr, Type) dsInnerListComp (stmts, bndrs) = do - expr <- dsListComp stmts (mkBigLHsVarTup bndrs) bndrs_tuple_type - return (expr, bndrs_tuple_type) - where - bndrs_types = map idType bndrs - bndrs_tuple_type = mkBigCoreTupTy bndrs_types - + = do { expr <- dsListComp (stmts ++ [noLoc $ mkLastStmt (mkBigLHsVarTup bndrs)]) + bndrs_tuple_type + ; return (expr, bndrs_tuple_type) } + where + bndrs_tuple_type = mkBigCoreVarTupTy bndrs -- This function factors out commonality between the desugaring strategies for TransformStmt. -- Given such a statement it gives you back an expression representing how to compute the transformed @@ -228,9 +227,40 @@ with the Unboxed variety. \begin{code} -deListComp :: [Stmt Id] -> LHsExpr Id -> CoreExpr -> DsM CoreExpr +deListComp :: [Stmt Id] -> CoreExpr -> DsM CoreExpr + +deListComp [] _ = panic "deListComp" -deListComp (ParStmt stmtss_w_bndrs _ _ _ : quals) body list +deListComp (LastStmt body _ : quals) list + = -- Figure 7.4, SLPJ, p 135, rule C above + ASSERT( null quals ) + do { core_body <- dsLExpr body + ; return (mkConsExpr (exprType core_body) core_body list) } + + -- Non-last: must be a guard +deListComp (ExprStmt guard _ _ _ : quals) list = do -- rule B above + core_guard <- dsLExpr guard + core_rest <- deListComp quals list + return (mkIfThenElse core_guard core_rest list) + +-- [e | let B, qs] = let B in [e | qs] +deListComp (LetStmt binds : quals) list = do + core_rest <- deListComp quals list + dsLocalBinds binds core_rest + +deListComp (stmt@(TransformStmt {}) : quals) list = do + (inner_list_expr, pat) <- dsTransformStmt stmt + deBindComp pat inner_list_expr quals list + +deListComp (stmt@(GroupStmt {}) : quals) list = do + (inner_list_expr, pat) <- dsGroupStmt stmt + deBindComp pat inner_list_expr quals list + +deListComp (BindStmt pat list1 _ _ : quals) core_list2 = do -- rule A' above + core_list1 <- dsLExpr list1 + deBindComp pat core_list1 quals core_list2 + +deListComp (ParStmt stmtss_w_bndrs _ _ _ : quals) list = do exps_and_qual_tys <- mapM dsInnerListComp stmtss_w_bndrs let (exps, qual_tys) = unzip exps_and_qual_tys @@ -239,7 +269,7 @@ deListComp (ParStmt stmtss_w_bndrs _ _ _ : quals) body list -- Deal with [e | pat <- zip l1 .. ln] in example above deBindComp pat (Let (Rec [(zip_fn, zip_rhs)]) (mkApps (Var zip_fn) exps)) - quals body list + quals list where bndrs_s = map snd stmtss_w_bndrs @@ -247,34 +277,6 @@ deListComp (ParStmt stmtss_w_bndrs _ _ _ : quals) body list -- pat is the pattern ((x1,..,xn), (y1,..,ym)) in the example above pat = mkBigLHsPatTup pats pats = map mkBigLHsVarPatTup bndrs_s - - -- Last: the one to return -deListComp [] body list = do -- Figure 7.4, SLPJ, p 135, rule C above - core_body <- dsLExpr body - return (mkConsExpr (exprType core_body) core_body list) - - -- Non-last: must be a guard -deListComp (ExprStmt guard _ _ _ : quals) body list = do -- rule B above - core_guard <- dsLExpr guard - core_rest <- deListComp quals body list - return (mkIfThenElse core_guard core_rest list) - --- [e | let B, qs] = let B in [e | qs] -deListComp (LetStmt binds : quals) body list = do - core_rest <- deListComp quals body list - dsLocalBinds binds core_rest - -deListComp (stmt@(TransformStmt {}) : quals) body list = do - (inner_list_expr, pat) <- dsTransformStmt stmt - deBindComp pat inner_list_expr quals body list - -deListComp (stmt@(GroupStmt {}) : quals) body list = do - (inner_list_expr, pat) <- dsGroupStmt stmt - deBindComp pat inner_list_expr quals body list - -deListComp (BindStmt pat list1 _ _ : quals) body core_list2 = do -- rule A' above - core_list1 <- dsLExpr list1 - deBindComp pat core_list1 quals body core_list2 \end{code} @@ -282,10 +284,9 @@ deListComp (BindStmt pat list1 _ _ : quals) body core_list2 = do -- rule A' abov deBindComp :: OutPat Id -> CoreExpr -> [Stmt Id] - -> LHsExpr Id -> CoreExpr -> DsM (Expr Id) -deBindComp pat core_list1 quals body core_list2 = do +deBindComp pat core_list1 quals core_list2 = do let u3_ty@u1_ty = exprType core_list1 -- two names, same thing @@ -302,7 +303,7 @@ deBindComp pat core_list1 quals body core_list2 = do core_fail = App (Var h) (Var u3) letrec_body = App (Var h) core_list1 - rest_expr <- deListComp quals body core_fail + rest_expr <- deListComp quals core_fail core_match <- matchSimply (Var u2) (StmtCtxt ListComp) pat rest_expr core_fail let @@ -337,48 +338,48 @@ TE[ e | p <- l , q ] c n = let \begin{code} dfListComp :: Id -> Id -- 'c' and 'n' -> [Stmt Id] -- the rest of the qual's - -> LHsExpr Id -> DsM CoreExpr - -- Last: the one to return -dfListComp c_id n_id [] body = do - core_body <- dsLExpr body - return (mkApps (Var c_id) [core_body, Var n_id]) +dfListComp _ _ [] = panic "dfListComp" + +dfListComp c_id n_id (LastStmt body _ : quals) + = ASSERT( null quals ) + do { core_body <- dsLExpr body + ; return (mkApps (Var c_id) [core_body, Var n_id]) } -- Non-last: must be a guard -dfListComp c_id n_id (ExprStmt guard _ _ _ : quals) body = do +dfListComp c_id n_id (ExprStmt guard _ _ _ : quals) = do core_guard <- dsLExpr guard - core_rest <- dfListComp c_id n_id quals body + core_rest <- dfListComp c_id n_id quals return (mkIfThenElse core_guard core_rest (Var n_id)) -dfListComp c_id n_id (LetStmt binds : quals) body = do +dfListComp c_id n_id (LetStmt binds : quals) = do -- new in 1.3, local bindings - core_rest <- dfListComp c_id n_id quals body + core_rest <- dfListComp c_id n_id quals dsLocalBinds binds core_rest -dfListComp c_id n_id (stmt@(TransformStmt {}) : quals) body = do +dfListComp c_id n_id (stmt@(TransformStmt {}) : quals) = do (inner_list_expr, pat) <- dsTransformStmt stmt -- Anyway, we bind the newly transformed list via the generic binding function - dfBindComp c_id n_id (pat, inner_list_expr) quals body + dfBindComp c_id n_id (pat, inner_list_expr) quals -dfListComp c_id n_id (stmt@(GroupStmt {}) : quals) body = do +dfListComp c_id n_id (stmt@(GroupStmt {}) : quals) = do (inner_list_expr, pat) <- dsGroupStmt stmt -- Anyway, we bind the newly grouped list via the generic binding function - dfBindComp c_id n_id (pat, inner_list_expr) quals body + dfBindComp c_id n_id (pat, inner_list_expr) quals -dfListComp c_id n_id (BindStmt pat list1 _ _ : quals) body = do +dfListComp c_id n_id (BindStmt pat list1 _ _ : quals) = do -- evaluate the two lists core_list1 <- dsLExpr list1 -- Do the rest of the work in the generic binding builder - dfBindComp c_id n_id (pat, core_list1) quals body + dfBindComp c_id n_id (pat, core_list1) quals dfBindComp :: Id -> Id -- 'c' and 'n' -> (LPat Id, CoreExpr) -> [Stmt Id] -- the rest of the qual's - -> LHsExpr Id -> DsM CoreExpr -dfBindComp c_id n_id (pat, core_list1) quals body = do +dfBindComp c_id n_id (pat, core_list1) quals = do -- find the required type let x_ty = hsLPatType pat b_ty = idType n_id @@ -387,7 +388,7 @@ dfBindComp c_id n_id (pat, core_list1) quals body = do [b, x] <- newSysLocalsDs [b_ty, x_ty] -- build rest of the comprehesion - core_rest <- dfListComp c_id b quals body + core_rest <- dfListComp c_id b quals -- build the pattern match core_expr <- matchSimply (Var x) (StmtCtxt ListComp) @@ -482,9 +483,6 @@ mkUnzipBind elt_tys = do unzip_fn_ty = elt_tuple_list_ty `mkFunTy` elt_list_tuple_ty mkConcatExpression (list_element_ty, head, tail) = mkConsExpr list_element_ty head tail - - - \end{code} %************************************************************************ @@ -500,11 +498,10 @@ mkUnzipBind elt_tys = do -- [:e | qss:] = <<[:e | qss:]>> () [:():] -- dsPArrComp :: [Stmt Id] - -> LHsExpr Id - -> Type -- Don't use; called with `undefined' below -> DsM CoreExpr -dsPArrComp [ParStmt qss _ _ _] body _ = -- parallel comprehension - dePArrParComp qss body + +-- Special case for parallel comprehension +dsPArrComp (ParStmt qss _ _ _ : quals) = dePArrParComp qss quals -- Special case for simple generators: -- @@ -515,7 +512,7 @@ dsPArrComp [ParStmt qss _ _ _] body _ = -- parallel comprehension -- <<[:e' | p <- e, qs:]>> = -- <<[:e' | qs:]>> p (filterP (\x -> case x of {p -> True; _ -> False}) e) -- -dsPArrComp (BindStmt p e _ _ : qs) body _ = do +dsPArrComp (BindStmt p e _ _ : qs) = do filterP <- dsLookupDPHId filterPName ce <- dsLExpr e let ety'ce = parrElemType ce @@ -525,38 +522,41 @@ dsPArrComp (BindStmt p e _ _ : qs) body _ = do pred <- matchSimply (Var v) (StmtCtxt PArrComp) p true false let gen | isIrrefutableHsPat p = ce | otherwise = mkApps (Var filterP) [Type ety'ce, mkLams [v] pred, ce] - dePArrComp qs body p gen + dePArrComp qs p gen -dsPArrComp qs body _ = do -- no ParStmt in `qs' +dsPArrComp qs = do -- no ParStmt in `qs' sglP <- dsLookupDPHId singletonPName let unitArray = mkApps (Var sglP) [Type unitTy, mkCoreTup []] - dePArrComp qs body (noLoc $ WildPat unitTy) unitArray + dePArrComp qs (noLoc $ WildPat unitTy) unitArray -- the work horse -- dePArrComp :: [Stmt Id] - -> LHsExpr Id -> LPat Id -- the current generator pattern -> CoreExpr -- the current generator expression -> DsM CoreExpr + +dePArrComp [] _ _ = panic "dePArrComp" + -- -- <<[:e' | :]>> pa ea = mapP (\pa -> e') ea -- -dePArrComp [] e' pa cea = do - mapP <- dsLookupDPHId mapPName - let ty = parrElemType cea - (clam, ty'e') <- deLambda ty pa e' - return $ mkApps (Var mapP) [Type ty, Type ty'e', clam, cea] +dePArrComp (LastStmt e' _ : quals) pa cea + = ASSERT( null quals ) + do { mapP <- dsLookupDPHId mapPName + ; let ty = parrElemType cea + ; (clam, ty'e') <- deLambda ty pa e' + ; return $ mkApps (Var mapP) [Type ty, Type ty'e', clam, cea] } -- -- <<[:e' | b, qs:]>> pa ea = <<[:e' | qs:]>> pa (filterP (\pa -> b) ea) -- -dePArrComp (ExprStmt b _ _ _ : qs) body pa cea = do +dePArrComp (ExprStmt b _ _ _ : qs) pa cea = do filterP <- dsLookupDPHId filterPName let ty = parrElemType cea (clam,_) <- deLambda ty pa b - dePArrComp qs body pa (mkApps (Var filterP) [Type ty, clam, cea]) + dePArrComp qs pa (mkApps (Var filterP) [Type ty, clam, cea]) -- -- <<[:e' | p <- e, qs:]>> pa ea = @@ -571,7 +571,7 @@ dePArrComp (ExprStmt b _ _ _ : qs) body pa cea = do -- in -- <<[:e' | qs:]>> (pa, p) (crossMapP ea ef) -- -dePArrComp (BindStmt p e _ _ : qs) body pa cea = do +dePArrComp (BindStmt p e _ _ : qs) pa cea = do filterP <- dsLookupDPHId filterPName crossMapP <- dsLookupDPHId crossMapPName ce <- dsLExpr e @@ -587,7 +587,7 @@ dePArrComp (BindStmt p e _ _ : qs) body pa cea = do let ety'cef = ety'ce -- filter doesn't change the element type pa' = mkLHsPatTup [pa, p] - dePArrComp qs body pa' (mkApps (Var crossMapP) + dePArrComp qs pa' (mkApps (Var crossMapP) [Type ety'cea, Type ety'cef, cea, clam]) -- -- <<[:e' | let ds, qs:]>> pa ea = @@ -596,7 +596,7 @@ dePArrComp (BindStmt p e _ _ : qs) body pa cea = do -- where -- {x_1, ..., x_n} = DV (ds) -- Defined Variables -- -dePArrComp (LetStmt ds : qs) body pa cea = do +dePArrComp (LetStmt ds : qs) pa cea = do mapP <- dsLookupDPHId mapPName let xs = collectLocalBinders ds ty'cea = parrElemType cea @@ -611,14 +611,14 @@ dePArrComp (LetStmt ds : qs) body pa cea = do ccase <- matchSimply (Var v) (StmtCtxt PArrComp) pa projBody cerr let pa' = mkLHsPatTup [pa, mkLHsPatTup (map nlVarPat xs)] proj = mkLams [v] ccase - dePArrComp qs body pa' (mkApps (Var mapP) + dePArrComp qs pa' (mkApps (Var mapP) [Type ty'cea, Type errTy, proj, cea]) -- -- The parser guarantees that parallel comprehensions can only appear as -- singeltons qualifier lists, which we already special case in the caller. -- So, encountering one here is a bug. -- -dePArrComp (ParStmt _ _ _ _ : _) _ _ _ = +dePArrComp (ParStmt _ _ _ _ : _) _ _ = panic "DsListComp.dePArrComp: malformed comprehension AST" -- <<[:e' | qs | qss:]>> pa ea = @@ -627,17 +627,17 @@ dePArrComp (ParStmt _ _ _ _ : _) _ _ _ = -- where -- {x_1, ..., x_n} = DV (qs) -- -dePArrParComp :: [([LStmt Id], [Id])] -> LHsExpr Id -> DsM CoreExpr -dePArrParComp qss body = do +dePArrParComp :: [([LStmt Id], [Id])] -> [Stmt Id] -> DsM CoreExpr +dePArrParComp qss quals = do (pQss, ceQss) <- deParStmt qss - dePArrComp [] body pQss ceQss + dePArrComp quals pQss ceQss where deParStmt [] = -- empty parallel statement lists have no source representation panic "DsListComp.dePArrComp: Empty parallel list comprehension" deParStmt ((qs, xs):qss) = do -- first statement let res_expr = mkLHsVarTuple xs - cqs <- dsPArrComp (map unLoc qs) res_expr undefined + cqs <- dsPArrComp (map unLoc qs ++ [mkLastStmt res_expr]) parStmts qss (mkLHsVarPatTup xs) cqs --- parStmts [] pa cea = return (pa, cea) @@ -646,7 +646,7 @@ dePArrParComp qss body = do let pa' = mkLHsPatTup [pa, mkLHsVarPatTup xs] ty'cea = parrElemType cea res_expr = mkLHsVarTuple xs - cqs <- dsPArrComp (map unLoc qs) res_expr undefined + cqs <- dsPArrComp (map unLoc qs ++ [mkLastStmt res_expr]) let ty'cqs = parrElemType cqs cea' = mkApps (Var zipP) [Type ty'cea, Type ty'cqs, cea, cqs] parStmts qss pa' cea' @@ -701,11 +701,9 @@ data DsMonadComp = DsMonadComp -- Entry point for monad comprehension desugaring -- dsMonadComp :: [LStmt Id] -- the statements - -> SyntaxExpr Id -- the "return" function - -> LHsExpr Id -- the body -> Type -- the final type -> DsM CoreExpr -dsMonadComp stmts return_op body res_ty +dsMonadComp stmts res_ty = dsMcStmts stmts (DsMonadComp (Left return_op) body m_ty) where (m_ty, _) = tcSplitAppTy res_ty @@ -729,30 +727,33 @@ dsMcStmts ((L loc stmt) : lstmts) mc = putSrcSpanDs loc (dsMcStmt stmt lstmts mc) -dsMcStmt :: Stmt Id - -> [LStmt Id] - -> DsMonadComp - -> DsM CoreExpr +dsMcStmt :: Stmt Id -> [LStmt Id] -> DsM CoreExpr + +dsMcStmt (LastStmt body ret_op) stmts + = ASSERT( null stmts ) + do { body' <- dsLExpr body + ; ret_op' <- dsExpr ret_op + ; return (App ret_op' body') } -- [ .. | let binds, stmts ] -dsMcStmt (LetStmt binds) stmts mc - = do { rest <- dsMcStmts stmts mc +dsMcStmt (LetStmt binds) stmts + = do { rest <- dsMcStmts stmts ; dsLocalBinds binds rest } -- [ .. | a <- m, stmts ] -dsMcStmt (BindStmt pat rhs bind_op fail_op) stmts mc - = do { rhs' <- dsLExpr rhs - ; dsMcBindStmt pat rhs' bind_op fail_op stmts mc } +dsMcStmt (BindStmt pat rhs bind_op fail_op) stmts + = do { rhs' <- dsLExpr rhs + ; dsMcBindStmt pat rhs' bind_op fail_op stmts } -- Apply `guard` to the `exp` expression -- -- [ .. | exp, stmts ] -- -dsMcStmt (ExprStmt exp then_exp guard_exp _) stmts mc +dsMcStmt (ExprStmt exp then_exp guard_exp _) stmts = do { exp' <- dsLExpr exp ; guard_exp' <- dsExpr guard_exp ; then_exp' <- dsExpr then_exp - ; rest <- dsMcStmts stmts mc + ; rest <- dsMcStmts stmts ; return $ mkApps then_exp' [ mkApps guard_exp' [exp'] , rest ] } @@ -762,26 +763,38 @@ dsMcStmt (ExprStmt exp then_exp guard_exp _) stmts mc -- -- where [| qs |] is the desugared inner monad comprehenion generated by the -- statements `qs`. -dsMcStmt (TransformStmt stmts binders usingExpr maybeByExpr return_op bind_op) stmts_rest mc - = do { (expr, _) <- dsInnerMonadComp (stmts, binders) (mc { mc_return = Left return_op }) - ; let binders_tuple_type = mkBigCoreTupTy $ map idType binders +dsMcStmt (TransformStmt stmts binders usingExpr maybeByExpr return_op bind_op) stmts_rest + = do { expr <- dsInnerMonadComp stmts binders return_op + ; let binders_tup_type = mkBigCoreTupTy $ map idType binders ; usingExpr' <- dsLExpr usingExpr ; using_args <- case maybeByExpr of Nothing -> return [expr] Just byExpr -> do byExpr' <- dsLExpr byExpr us <- newUniqueSupply - tuple_binder <- newSysLocalDs binders_tuple_type - let byExprWrapper = mkTupleCase us binders byExpr' tuple_binder (Var tuple_binder) - return [Lam tuple_binder byExprWrapper, expr] + tup_binder <- newSysLocalDs binders_tup_type + let byExprWrapper = mkTupleCase us binders byExpr' tup_binder (Var tup_binder) + return [Lam tup_binder byExprWrapper, expr] ; let pat = mkBigLHsVarPatTup binders - rhs = mkApps usingExpr' ((Type binders_tuple_type) : using_args) + rhs = mkApps usingExpr' ((Type binders_tup_type) : using_args) - ; dsMcBindStmt pat rhs bind_op noSyntaxExpr stmts_rest mc } + ; dsMcBindStmt pat rhs bind_op noSyntaxExpr stmts_rest } -- Group statements desugar like this: -- +-- [| (q, then group by e using f); rest |] +-- ---> f {qt} (\qv -> e) [| q; return qv |] >>= \ n_tup -> +-- case unzip n_tup of qv -> [| rest |] +-- +-- where variables (v1:t1, ..., vk:tk) are bound by q +-- qv = (v1, ..., vk) +-- qt = (t1, ..., tk) +-- (>>=) :: m2 a -> (a -> m3 b) -> m3 b +-- f :: forall a. (a -> t) -> m1 a -> m2 (n a) +-- n_tup :: n qt +-- unzip :: n qt -> (n t1, ..., n tk) (needs Functor n) +-- -- [| q, then group by e using f |] -> (f (\q_v -> e) [| q |]) >>= (return . (unzip q_v)) -- -- which is equal to @@ -790,24 +803,23 @@ dsMcStmt (TransformStmt stmts binders usingExpr maybeByExpr return_op bind_op) s -- -- where unzip is of the form -- --- unzip :: m (a,b,c,..) -> (m a,m b,m c,..) --- unzip m_tuple = ( liftM selN1 m_tuple --- , liftM selN2 m_tuple +-- unzip :: n (a,b,c,..) -> (n a,n b,n c,..) +-- unzip m_tuple = ( fmap selN1 m_tuple +-- , fmap selN2 m_tuple -- , .. ) -- where selN1 (a,b,c,..) = a -- selN2 (a,b,c,..) = b -- .. -- -dsMcStmt (GroupStmt stmts binderMap by using return_op bind_op liftM_op) stmts_rest mc +dsMcStmt (GroupStmt stmts binderMap by using return_op bind_op fmap_op) stmts_rest = do { let (fromBinders, toBinders) = unzip binderMap - fromBindersTypes = map idType fromBinders + fromBindersTypes = map idType fromBinders -- Types ty fromBindersTupleTy = mkBigCoreTupTy fromBindersTypes - toBindersTypes = map idType toBinders + toBindersTypes = map idType toBinders -- Types (n ty) toBindersTupleTy = mkBigCoreTupTy toBindersTypes - m_ty = mc_m_ty mc -- Desugar an inner comprehension which outputs a list of tuples of the "from" binders - ; (expr, _) <- dsInnerMonadComp (stmts, fromBinders) (mc { mc_return = Left return_op }) + ; expr <- dsInnerMonadComp stmts fromBinders return_op -- Work out what arguments should be supplied to that expression: i.e. is an extraction -- function required? If so, create that desugared function and add to arguments @@ -815,62 +827,45 @@ dsMcStmt (GroupStmt stmts binderMap by using return_op bind_op liftM_op) stmts_r ; usingArgs <- case by of Nothing -> return [expr] Just by_e -> do { by_e' <- dsLExpr by_e - ; us <- newUniqueSupply - ; from_tup_id <- newSysLocalDs fromBindersTupleTy - ; let by_wrap = mkTupleCase us fromBinders by_e' - from_tup_id (Var from_tup_id) - ; return [Lam from_tup_id by_wrap, expr] } + ; lam <- matchTuple fromBinders by_e' + ; return [lam, expr] } -- Create an unzip function for the appropriate arity and element types - ; liftM_op' <- dsExpr liftM_op - ; (unzip_fn, unzip_rhs) <- mkMcUnzipM liftM_op' m_ty fromBindersTypes + ; fmap_op' <- dsExpr fmap_op + ; (unzip_fn, unzip_rhs) <- mkMcUnzipM fmap_op' m_ty fromBindersTypes -- Generate the expressions to build the grouped list - - ; let -- First we apply the grouping function to the inner monad - inner_monad_expr = mkApps usingExpr' ((Type fromBindersTupleTy) : usingArgs) - -- Then we map our "unzip" across it to turn the "monad of tuples" into "tuples of monads" - -- We make sure we instantiate the type variable "a" to be a "monad of 'from' tuples" and - -- the "b" to be a "tuple of 'to' monads"! - unzipped_inner_monad_expr = mkApps liftM_op' -- ! - -- Types: - [ Type (m_ty `mkAppTy` fromBindersTupleTy), Type toBindersTupleTy - -- And arguments: - , Var unzip_fn, inner_monad_expr ] - -- Then finally we bind the unzip function around that expression - bound_unzipped_inner_monad_expr = Let (Rec [(unzip_fn, unzip_rhs)]) unzipped_inner_monad_expr - - -- Build a pattern that ensures the consumer binds into the NEW binders, which hold monads - -- rather than single values - ; let pat = mkBigLHsVarPatTup toBinders - rhs = bound_unzipped_inner_monad_expr - - ; dsMcBindStmt pat rhs bind_op noSyntaxExpr stmts_rest mc } + -- Build a pattern that ensures the consumer binds into the NEW binders, + -- which hold monads rather than single values + ; bind_op' <- dsExpr bind_op + ; let bind_ty = exprType bind_op' -- m2 (n (a,b,c)) -> (n (a,b,c) -> r1) -> r2 + n_tup_ty = funArgTy $ funArgTy $ funResultTy bind_ty + + ; body <- dsMcStmts stmts_rest + ; n_tup_var <- newSysLocalDs n_tup_ty + ; tup_n_var <- newSysLocalDs (mkBigCoreVarTupTy toBinders) + ; us <- newUniqueSupply + ; let unzip_n_tup = Let (Rec [(unzip_fn, unzip_rhs)]) $ + App (Var unzip_fn) (Var n_tup_var) + -- unzip_n_tup :: (n a, n b, n c) + body' = mkTupleCase us toBinders body unzip_n_tup (Var tup_n_var) + + ; return (mkApps bind_op' [rhs', Lam n_tup_var body']) } -- Parallel statements. Use `Control.Monad.Zip.mzip` to zip parallel -- statements, for example: -- -- [ body | qs1 | qs2 | qs3 ] --- -> [ body | (bndrs1, (bndrs2, bndrs3)) <- mzip qs1 (mzip qs2 qs3) ] --- --- where `mzip` is of the form +-- -> [ body | (bndrs1, (bndrs2, bndrs3)) +-- <- [bndrs1 | qs1] `mzip` ([bndrs2 | qs2] `mzip` [bndrs3 | qs3]) ] -- --- mzip :: m a -> m b -> m (a,b) --- -dsMcStmt (ParStmt pairs mzip_op bind_op return_op) stmts_rest mc - = do { -- Get types for `return` - return_op' <- dsExpr return_op - ; let pairs_with_return = map (\tp@(_,b) -> (mkReturn b,tp)) pairs - mkReturn bndrs = mkApps return_op' [Type (mkBigCoreTupTy (map idType bndrs))] - - ; pairs' <- mapM (\(r,tp) -> dsInnerMonadComp tp mc{mc_return = Right r}) - pairs_with_return - - ; let (exps, _qual_tys) = unzip pairs' - -- Types of our `Id`s are getting messed up by `dsInnerMonadComp` - -- so we construct them by hand: - qual_tys = map (mkBigCoreTupTy . map idType . snd) pairs +-- where `mzip` has type +-- mzip :: forall a b. m a -> m b -> m (a,b) +-- NB: we need a polymorphic mzip because we call it several times +dsMcStmt (ParStmt pairs mzip_op bind_op return_op) stmts_rest + = do { exps <- mapM ds_inner pairs + ; let qual_tys = map (mkBigCoreVarTupTy . snd) pairs ; mzip_op' <- dsExpr mzip_op ; (zip_fn, zip_rhs) <- mkMcZipM mzip_op' (mc_m_ty mc) qual_tys @@ -881,9 +876,23 @@ dsMcStmt (ParStmt pairs mzip_op bind_op return_op) stmts_rest mc pat = foldr (\tn tm -> mkBigLHsPatTup [tn, tm]) (last vars) (init vars) rhs = Let (Rec [(zip_fn, zip_rhs)]) (mkApps (Var zip_fn) exps) - ; dsMcBindStmt pat rhs bind_op noSyntaxExpr stmts_rest mc } + ; dsMcBindStmt pat rhs bind_op noSyntaxExpr stmts_rest } + where + ds_inner (stmts, bndrs) = dsInnerMonadComp stmts bndrs mono_ret_op + where + mono_ret_op = HsWrap (WpTyApp (mkBigCoreVarTupTy bndrs)) return_op -dsMcStmt stmt _ _ = pprPanic "dsMcStmt: unexpected stmt" (ppr stmt) +dsMcStmt stmt _ = pprPanic "dsMcStmt: unexpected stmt" (ppr stmt) + + +matchTuple :: [Id] -> CoreExpr -> DsM CoreExpr +-- (matchTuple [a,b,c] body) +-- returns the Core term +-- \x. case x of (a,b,c) -> body +matchTuple ids body + = do { us <- newUniqueSupply + ; tup_id <- newSysLocalDs (mkBigLHsVarPatTup ids) + ; return (Lam tup_id $ mkTupleCase us ids body tup_id (Var tup_id)) } -- general `rhs' >>= \pat -> stmts` desugaring where `rhs'` is already a @@ -893,10 +902,9 @@ dsMcBindStmt :: LPat Id -> SyntaxExpr Id -> SyntaxExpr Id -> [LStmt Id] - -> DsMonadComp -> DsM CoreExpr -dsMcBindStmt pat rhs' bind_op fail_op stmts mc - = do { body <- dsMcStmts stmts mc +dsMcBindStmt pat rhs' bind_op fail_op stmts + = do { body <- dsMcStmts stmts ; bind_op' <- dsExpr bind_op ; var <- selectSimpleMatchVarL pat ; let bind_ty = exprType bind_op' -- rhs -> (pat -> res1) -> res2 @@ -922,16 +930,16 @@ dsMcBindStmt pat rhs' bind_op fail_op stmts mc showSDoc (ppr (getLoc pat)) -- Desugar nested monad comprehensions, for example in `then..` constructs -dsInnerMonadComp :: ([LStmt Id], [Id]) - -> DsMonadComp - -> DsM (CoreExpr, Type) -dsInnerMonadComp (stmts, bndrs) DsMonadComp{ mc_return, mc_m_ty } - = do { expr <- dsMcStmts stmts mc' - ; return (expr, bndrs_tuple_type) } - where - bndrs_types = map idType bndrs - bndrs_tuple_type = mkAppTy mc_m_ty $ mkBigCoreTupTy bndrs_types - mc' = DsMonadComp mc_return (mkBigLHsVarTup bndrs) mc_m_ty +-- dsInnerMonadComp quals [a,b,c] ret_op +-- returns the desugaring of +-- [ (a,b,c) | quals ] + +dsInnerMonadComp :: [LStmt Id] + -> [Id] -- Return a tuple of these variables + -> LHsExpr Id -- The monomorphic "return" operator + -> DsM CoreExpr +dsInnerMonadComp stmts bndrs ret_op + = dsMcStmts (stmts ++ [noLoc (ReturnStmt (mkBigLHsVarTup bndrs) ret_op)]) -- The `unzip` function for `GroupStmt` in a monad comprehensions --