X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsListComp.lhs;h=63cae938d083cf5b061ccd87a272e3fc69999801;hp=7fc4fb9654c62d9579a0be8edabbe522bf704841;hb=d76d9636aeebe933d160157331b8c8c0087e73ac;hpb=7fc749a43b4b6b85d234fa95d4928648259584f4 diff --git a/compiler/deSugar/DsListComp.lhs b/compiler/deSugar/DsListComp.lhs index 7fc4fb9..63cae93 100644 --- a/compiler/deSugar/DsListComp.lhs +++ b/compiler/deSugar/DsListComp.lhs @@ -3,41 +3,42 @@ % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % -Desugaring list comprehensions and array comprehensions +Desugaring list comprehensions, monad comprehensions and array comprehensions \begin{code} -{-# OPTIONS -w #-} +{-# LANGUAGE NamedFieldPuns #-} +{-# OPTIONS -fno-warn-incomplete-patterns #-} -- The above warning supression flag is a temporary kludge. -- While working on this module you are encouraged to remove it and fix -- any warnings in the module. See -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings -- for details -module DsListComp ( dsListComp, dsPArrComp ) where +module DsListComp ( dsListComp, dsPArrComp, dsMonadComp ) where #include "HsVersions.h" -import {-# SOURCE #-} DsExpr ( dsLExpr, dsLocalBinds ) +import {-# SOURCE #-} DsExpr ( dsExpr, dsLExpr, dsLocalBinds ) -import BasicTypes import HsSyn import TcHsSyn import CoreSyn +import MkCore import DsMonad -- the monadery used in the desugarer import DsUtils import DynFlags import CoreUtils -import Var +import Id import Type -import TysPrim import TysWiredIn import Match import PrelNames -import PrelInfo import SrcLoc -import Panic +import Outputable +import FastString +import TcType \end{code} List comprehensions may be desugared in one of two ways: ``ordinary'' @@ -48,38 +49,119 @@ 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 - = getDOptsDs `thenDs` \dflags -> - let - quals = map unLoc lquals - in - if not (dopt Opt_RewriteRules dflags) || dopt Opt_IgnoreInterfacePragmas dflags - -- Either rules are switched off, or we are ignoring what there are; - -- Either way foldr/build won't happen, so use the more efficient - -- Wadler-style desugaring - || isParallelComp quals - -- Foldr-style desugaring can't handle - -- parallel list comprehensions - then deListComp quals body (mkNilExpr elt_ty) - - else -- Foldr/build should be enabled, so desugar - -- into foldrs and builds - newTyVarsDs [alphaTyVar] `thenDs` \ [n_tyvar] -> - let - n_ty = mkTyVarTy n_tyvar - c_ty = mkFunTys [elt_ty, n_ty] n_ty - in - newSysLocalsDs [c_ty,n_ty] `thenDs` \ [c, n] -> - dfListComp c n quals body `thenDs` \ result -> - dsLookupGlobalId buildName `thenDs` \ build_id -> - returnDs (Var build_id `App` Type elt_ty - `App` mkLams [n_tyvar, c, n] result) - - where isParallelComp (ParStmt bndrstmtss : _) = True - isParallelComp _ = False +dsListComp lquals res_ty = do + dflags <- getDOptsDs + let quals = map unLoc lquals + elt_ty = case tcTyConAppArgs res_ty of + [elt_ty] -> elt_ty + _ -> pprPanic "dsListComp" (ppr res_ty $$ ppr lquals) + + if not (dopt Opt_EnableRewriteRules dflags) || dopt Opt_IgnoreInterfacePragmas dflags + -- Either rules are switched off, or we are ignoring what there are; + -- Either way foldr/build won't happen, so use the more efficient + -- Wadler-style desugaring + || isParallelComp quals + -- Foldr-style desugaring can't handle parallel list comprehensions + 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 + + where + -- We must test for ParStmt anywhere, not just at the head, because an extension + -- to list comprehensions would be to add brackets to specify the associativity + -- of qualifier lists. This is really easy to do by adding extra ParStmts into the + -- mix of possibly a single element in length, so we do this to leave the possibility open + isParallelComp = any isParallelStmt + + isParallelStmt (ParStmt _ _ _ _) = True + isParallelStmt _ = False + + +-- This function lets you desugar a inner list comprehension and a list of the binders +-- of that comprehension that we need in the outer comprehension into such an expression +-- 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 ++ [noLoc $ mkLastStmt (mkBigLHsVarTup bndrs)]) + (mkListTy 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 +-- list and the tuple that you need to bind from that list in order to proceed with your desugaring +dsTransformStmt :: Stmt Id -> DsM (CoreExpr, LPat Id) +dsTransformStmt (TransformStmt stmts binders usingExpr maybeByExpr _ _) + = do { (expr, binders_tuple_type) <- dsInnerListComp (stmts, binders) + ; usingExpr' <- dsLExpr usingExpr + + ; using_args <- + case maybeByExpr of + Nothing -> return [expr] + Just byExpr -> do + byExpr' <- dsLExpr byExpr + + us <- newUniqueSupply + [tuple_binder] <- newSysLocalsDs [binders_tuple_type] + let byExprWrapper = mkTupleCase us binders byExpr' tuple_binder (Var tuple_binder) + + return [Lam tuple_binder byExprWrapper, expr] + + ; let inner_list_expr = mkApps usingExpr' ((Type binders_tuple_type) : using_args) + pat = mkBigLHsVarPatTup binders + ; return (inner_list_expr, pat) } + +-- This function factors out commonality between the desugaring strategies for GroupStmt. +-- Given such a statement it gives you back an expression representing how to compute the transformed +-- list and the tuple that you need to bind from that list in order to proceed with your desugaring +dsGroupStmt :: Stmt Id -> DsM (CoreExpr, LPat Id) +dsGroupStmt (GroupStmt { grpS_stmts = stmts, grpS_bndrs = binderMap + , grpS_by = by, grpS_using = using }) = do + let (fromBinders, toBinders) = unzip binderMap + + fromBindersTypes = map idType fromBinders + toBindersTypes = map idType toBinders + + toBindersTupleType = mkBigCoreTupTy toBindersTypes + + -- Desugar an inner comprehension which outputs a list of tuples of the "from" binders + (expr, from_tup_ty) <- dsInnerListComp (stmts, fromBinders) + + -- 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 + usingExpr' <- dsLExpr using + usingArgs <- case by of + Nothing -> return [expr] + Just by_e -> do { by_e' <- dsLExpr by_e + ; us <- newUniqueSupply + ; [from_tup_id] <- newSysLocalsDs [from_tup_ty] + ; let by_wrap = mkTupleCase us fromBinders by_e' + from_tup_id (Var from_tup_id) + ; return [Lam from_tup_id by_wrap, expr] } + + -- Create an unzip function for the appropriate arity and element types and find "map" + (unzip_fn, unzip_rhs) <- mkUnzipBind fromBindersTypes + map_id <- dsLookupGlobalId mapName + + -- Generate the expressions to build the grouped list + let -- First we apply the grouping function to the inner list + inner_list_expr = mkApps usingExpr' ((Type from_tup_ty) : usingArgs) + -- Then we map our "unzip" across it to turn the lists of tuples into tuples of lists + -- We make sure we instantiate the type variable "a" to be a list of "from" tuples and + -- the "b" to be a tuple of "to" lists! + unzipped_inner_list_expr = mkApps (Var map_id) + [Type (mkListTy from_tup_ty), Type toBindersTupleType, Var unzip_fn, inner_list_expr] + -- Then finally we bind the unzip function around that expression + bound_unzipped_inner_list_expr = Let (Rec [(unzip_fn, unzip_rhs)]) unzipped_inner_list_expr + + -- Build a pattern that ensures the consumer binds into the NEW binders, which hold lists rather than single values + let pat = mkBigLHsVarPatTup toBinders + return (bound_unzipped_inner_list_expr, pat) + \end{code} %************************************************************************ @@ -147,130 +229,96 @@ The introduced tuples are Boxed, but only because I couldn't get it to work with the Unboxed variety. \begin{code} -deListComp :: [Stmt Id] -> LHsExpr Id -> CoreExpr -> DsM CoreExpr -deListComp (ParStmt stmtss_w_bndrs : quals) body list - = mappM do_list_comp stmtss_w_bndrs `thenDs` \ exps -> - mkZipBind qual_tys `thenDs` \ (zip_fn, zip_rhs) -> +deListComp :: [Stmt Id] -> CoreExpr -> DsM CoreExpr - -- 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 +deListComp [] _ = panic "deListComp" - where - bndrs_s = map snd stmtss_w_bndrs +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) } - -- pat is the pattern ((x1,..,xn), (y1,..,ym)) in the example above - pat = mkTuplePat pats - pats = map mk_hs_tuple_pat bndrs_s + -- 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 - -- Types of (x1,..,xn), (y1,..,yn) etc - qual_tys = map mk_bndrs_tys bndrs_s +deListComp (stmt@(TransformStmt {}) : quals) list = do + (inner_list_expr, pat) <- dsTransformStmt stmt + deBindComp pat inner_list_expr quals list - do_list_comp (stmts, bndrs) - = dsListComp stmts (mk_hs_tuple_expr bndrs) - (mk_bndrs_tys bndrs) +deListComp (stmt@(GroupStmt {}) : quals) list = do + (inner_list_expr, pat) <- dsGroupStmt stmt + deBindComp pat inner_list_expr quals list - mk_bndrs_tys bndrs = mkCoreTupTy (map idType bndrs) +deListComp (BindStmt pat list1 _ _ : quals) core_list2 = do -- rule A' above + core_list1 <- dsLExpr list1 + deBindComp pat core_list1 quals core_list2 - -- Last: the one to return -deListComp [] body list -- Figure 7.4, SLPJ, p 135, rule C above - = dsLExpr body `thenDs` \ core_body -> - returnDs (mkConsExpr (exprType core_body) core_body list) +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 + + (zip_fn, zip_rhs) <- mkZipBind qual_tys - -- Non-last: must be a guard -deListComp (ExprStmt guard _ _ : quals) body list -- rule B above - = dsLExpr guard `thenDs` \ core_guard -> - deListComp quals body list `thenDs` \ core_rest -> - returnDs (mkIfThenElse core_guard core_rest 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 list --- [e | let B, qs] = let B in [e | qs] -deListComp (LetStmt binds : quals) body list - = deListComp quals body list `thenDs` \ core_rest -> - dsLocalBinds binds core_rest + where + bndrs_s = map snd stmtss_w_bndrs -deListComp (BindStmt pat list1 _ _ : quals) body core_list2 -- rule A' above - = dsLExpr list1 `thenDs` \ core_list1 -> - deBindComp pat core_list1 quals body core_list2 + -- pat is the pattern ((x1,..,xn), (y1,..,ym)) in the example above + pat = mkBigLHsPatTup pats + pats = map mkBigLHsVarPatTup bndrs_s \end{code} \begin{code} -deBindComp pat core_list1 quals body core_list2 - = let - u3_ty@u1_ty = exprType core_list1 -- two names, same thing +deBindComp :: OutPat Id + -> CoreExpr + -> [Stmt Id] + -> CoreExpr + -> DsM (Expr Id) +deBindComp pat core_list1 quals core_list2 = do + let + u3_ty@u1_ty = exprType core_list1 -- two names, same thing - -- u1_ty is a [alpha] type, and u2_ty = alpha - u2_ty = hsLPatType pat + -- u1_ty is a [alpha] type, and u2_ty = alpha + u2_ty = hsLPatType pat - res_ty = exprType core_list2 - h_ty = u1_ty `mkFunTy` res_ty - in - newSysLocalsDs [h_ty, u1_ty, u2_ty, u3_ty] `thenDs` \ [h, u1, u2, u3] -> + res_ty = exprType core_list2 + h_ty = u1_ty `mkFunTy` res_ty + + [h, u1, u2, u3] <- newSysLocalsDs [h_ty, u1_ty, u2_ty, u3_ty] -- the "fail" value ... let - core_fail = App (Var h) (Var u3) - letrec_body = App (Var h) core_list1 - in - deListComp quals body core_fail `thenDs` \ rest_expr -> - matchSimply (Var u2) (StmtCtxt ListComp) pat - rest_expr core_fail `thenDs` \ core_match -> + core_fail = App (Var h) (Var u3) + letrec_body = App (Var h) core_list1 + + rest_expr <- deListComp quals core_fail + core_match <- matchSimply (Var u2) (StmtCtxt ListComp) pat rest_expr core_fail + let - rhs = Lam u1 $ + rhs = Lam u1 $ Case (Var u1) u1 res_ty [(DataAlt nilDataCon, [], core_list2), (DataAlt consDataCon, [u2, u3], core_match)] -- Increasing order of tag - in - returnDs (Let (Rec [(h, rhs)]) letrec_body) -\end{code} - - -\begin{code} -mkZipBind :: [Type] -> DsM (Id, CoreExpr) --- mkZipBind [t1, t2] --- = (zip, \as1:[t1] as2:[t2] --- -> case as1 of --- [] -> [] --- (a1:as'1) -> case as2 of --- [] -> [] --- (a2:as'2) -> (a2,a2) : zip as'1 as'2)] - -mkZipBind elt_tys - = mappM newSysLocalDs list_tys `thenDs` \ ass -> - mappM newSysLocalDs elt_tys `thenDs` \ as' -> - mappM newSysLocalDs list_tys `thenDs` \ as's -> - newSysLocalDs zip_fn_ty `thenDs` \ zip_fn -> - let - inner_rhs = mkConsExpr ret_elt_ty - (mkCoreTup (map Var as')) - (mkVarApps (Var zip_fn) as's) - zip_body = foldr mk_case inner_rhs (zip3 ass as' as's) - in - returnDs (zip_fn, mkLams ass zip_body) - where - list_tys = map mkListTy elt_tys - ret_elt_ty = mkCoreTupTy elt_tys - list_ret_ty = mkListTy ret_elt_ty - zip_fn_ty = mkFunTys list_tys list_ret_ty - - mk_case (as, a', as') rest - = Case (Var as) as list_ret_ty - [(DataAlt nilDataCon, [], mkNilExpr ret_elt_ty), - (DataAlt consDataCon, [a', as'], rest)] - -- Increasing order of tag --- Helper functions that makes an HsTuple only for non-1-sized tuples -mk_hs_tuple_expr :: [Id] -> LHsExpr Id -mk_hs_tuple_expr [] = nlHsVar unitDataConId -mk_hs_tuple_expr [id] = nlHsVar id -mk_hs_tuple_expr ids = noLoc $ ExplicitTuple [ nlHsVar i | i <- ids ] Boxed - -mk_hs_tuple_pat :: [Id] -> LPat Id -mk_hs_tuple_pat bs = mkTuplePat (map nlVarPat bs) + + return (Let (Rec [(h, rhs)]) letrec_body) \end{code} - %************************************************************************ %* * \subsection[DsListComp-foldr-build]{Foldr/Build desugaring of list comprehensions} @@ -291,55 +339,153 @@ TE[ e | p <- l , q ] c n = let \end{verbatim} \begin{code} -dfListComp :: Id -> Id -- 'c' and 'n' - -> [Stmt Id] -- the rest of the qual's - -> LHsExpr Id - -> DsM CoreExpr +dfListComp :: Id -> Id -- 'c' and 'n' + -> [Stmt Id] -- the rest of the qual's + -> DsM CoreExpr + +dfListComp _ _ [] = panic "dfListComp" - -- Last: the one to return -dfListComp c_id n_id [] body - = dsLExpr body `thenDs` \ core_body -> - returnDs (mkApps (Var c_id) [core_body, Var n_id]) +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 - = dsLExpr guard `thenDs` \ core_guard -> - dfListComp c_id n_id quals body `thenDs` \ core_rest -> - returnDs (mkIfThenElse core_guard core_rest (Var n_id)) - -dfListComp c_id n_id (LetStmt binds : quals) body - -- new in 1.3, local bindings - = dfListComp c_id n_id quals body `thenDs` \ core_rest -> +dfListComp c_id n_id (ExprStmt guard _ _ _ : quals) = do + core_guard <- dsLExpr guard + 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) = do + -- new in 1.3, local bindings + core_rest <- dfListComp c_id n_id quals dsLocalBinds binds core_rest -dfListComp c_id n_id (BindStmt pat list1 _ _ : quals) body +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 + +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 + +dfListComp c_id n_id (BindStmt pat list1 _ _ : quals) = do -- evaluate the two lists - = dsLExpr list1 `thenDs` \ core_list1 -> - + core_list1 <- dsLExpr list1 + + -- Do the rest of the work in the generic binding builder + 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 + -> DsM CoreExpr +dfBindComp c_id n_id (pat, core_list1) quals = do -- find the required type let x_ty = hsLPatType pat - b_ty = idType n_id - in + b_ty = idType n_id -- create some new local id's - newSysLocalsDs [b_ty,x_ty] `thenDs` \ [b,x] -> + [b, x] <- newSysLocalsDs [b_ty, x_ty] -- build rest of the comprehesion - dfListComp c_id b quals body `thenDs` \ core_rest -> + core_rest <- dfListComp c_id b quals -- build the pattern match - matchSimply (Var x) (StmtCtxt ListComp) - pat core_rest (Var b) `thenDs` \ core_expr -> + core_expr <- matchSimply (Var x) (StmtCtxt ListComp) + pat core_rest (Var b) -- now build the outermost foldr, and return - dsLookupGlobalId foldrName `thenDs` \ foldr_id -> - returnDs ( - Var foldr_id `App` Type x_ty - `App` Type b_ty - `App` mkLams [x, b] core_expr - `App` Var n_id - `App` core_list1 - ) + mkFoldrExpr x_ty b_ty (mkLams [x, b] core_expr) (Var n_id) core_list1 +\end{code} + +%************************************************************************ +%* * +\subsection[DsFunGeneration]{Generation of zip/unzip functions for use in desugaring} +%* * +%************************************************************************ + +\begin{code} + +mkZipBind :: [Type] -> DsM (Id, CoreExpr) +-- mkZipBind [t1, t2] +-- = (zip, \as1:[t1] as2:[t2] +-- -> case as1 of +-- [] -> [] +-- (a1:as'1) -> case as2 of +-- [] -> [] +-- (a2:as'2) -> (a1, a2) : zip as'1 as'2)] + +mkZipBind elt_tys = do + ass <- mapM newSysLocalDs elt_list_tys + as' <- mapM newSysLocalDs elt_tys + as's <- mapM newSysLocalDs elt_list_tys + + zip_fn <- newSysLocalDs zip_fn_ty + + let inner_rhs = mkConsExpr elt_tuple_ty + (mkBigCoreVarTup as') + (mkVarApps (Var zip_fn) as's) + zip_body = foldr mk_case inner_rhs (zip3 ass as' as's) + + return (zip_fn, mkLams ass zip_body) + where + elt_list_tys = map mkListTy elt_tys + elt_tuple_ty = mkBigCoreTupTy elt_tys + elt_tuple_list_ty = mkListTy elt_tuple_ty + + zip_fn_ty = mkFunTys elt_list_tys elt_tuple_list_ty + + mk_case (as, a', as') rest + = Case (Var as) as elt_tuple_list_ty + [(DataAlt nilDataCon, [], mkNilExpr elt_tuple_ty), + (DataAlt consDataCon, [a', as'], rest)] + -- Increasing order of tag + + +mkUnzipBind :: [Type] -> DsM (Id, CoreExpr) +-- mkUnzipBind [t1, t2] +-- = (unzip, \ys :: [(t1, t2)] -> foldr (\ax :: (t1, t2) axs :: ([t1], [t2]) +-- -> case ax of +-- (x1, x2) -> case axs of +-- (xs1, xs2) -> (x1 : xs1, x2 : xs2)) +-- ([], []) +-- ys) +-- +-- We use foldr here in all cases, even if rules are turned off, because we may as well! +mkUnzipBind elt_tys = do + ax <- newSysLocalDs elt_tuple_ty + axs <- newSysLocalDs elt_list_tuple_ty + ys <- newSysLocalDs elt_tuple_list_ty + xs <- mapM newSysLocalDs elt_tys + xss <- mapM newSysLocalDs elt_list_tys + + unzip_fn <- newSysLocalDs unzip_fn_ty + + [us1, us2] <- sequence [newUniqueSupply, newUniqueSupply] + + let nil_tuple = mkBigCoreTup (map mkNilExpr elt_tys) + + concat_expressions = map mkConcatExpression (zip3 elt_tys (map Var xs) (map Var xss)) + tupled_concat_expression = mkBigCoreTup concat_expressions + + folder_body_inner_case = mkTupleCase us1 xss tupled_concat_expression axs (Var axs) + folder_body_outer_case = mkTupleCase us2 xs folder_body_inner_case ax (Var ax) + folder_body = mkLams [ax, axs] folder_body_outer_case + + unzip_body <- mkFoldrExpr elt_tuple_ty elt_list_tuple_ty folder_body nil_tuple (Var ys) + return (unzip_fn, mkLams [ys] unzip_body) + where + elt_tuple_ty = mkBigCoreTupTy elt_tys + elt_tuple_list_ty = mkListTy elt_tuple_ty + elt_list_tys = map mkListTy elt_tys + elt_list_tuple_ty = mkBigCoreTupTy elt_list_tys + + 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} %************************************************************************ @@ -354,74 +500,98 @@ dfListComp c_id n_id (BindStmt pat list1 _ _ : quals) body -- -- [: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 -dsPArrComp qs body _ = -- no ParStmt in `qs' - dsLookupGlobalId replicatePName `thenDs` \repP -> - let unitArray = mkApps (Var repP) [Type unitTy, - mkIntExpr 1, - mkCoreTup []] - in - dePArrComp qs body (mkTuplePat []) unitArray +dsPArrComp :: [Stmt Id] + -> DsM CoreExpr + +-- Special case for parallel comprehension +dsPArrComp (ParStmt qss _ _ _ : quals) = dePArrParComp qss quals + +-- Special case for simple generators: +-- +-- <<[:e' | p <- e, qs:]>> = <<[: e' | qs :]>> p e +-- +-- if matching again p cannot fail, or else +-- +-- <<[:e' | p <- e, qs:]>> = +-- <<[:e' | qs:]>> p (filterP (\x -> case x of {p -> True; _ -> False}) e) +-- +dsPArrComp (BindStmt p e _ _ : qs) = do + filterP <- dsLookupDPHId filterPName + ce <- dsLExpr e + let ety'ce = parrElemType ce + false = Var falseDataConId + true = Var trueDataConId + v <- newSysLocalDs ety'ce + 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 p gen + +dsPArrComp qs = do -- no ParStmt in `qs' + sglP <- dsLookupDPHId singletonPName + let unitArray = mkApps (Var sglP) [Type unitTy, mkCoreTup []] + 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 = - dsLookupGlobalId mapPName `thenDs` \mapP -> - let ty = parrElemType cea - in - deLambda ty pa e' `thenDs` \(clam, - ty'e') -> - returnDs $ 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 = - dsLookupGlobalId filterPName `thenDs` \filterP -> - let ty = parrElemType cea - in - deLambda ty pa b `thenDs` \(clam,_) -> - dePArrComp qs body pa (mkApps (Var filterP) [Type ty, clam, cea]) +dePArrComp (ExprStmt b _ _ _ : qs) pa cea = do + filterP <- dsLookupDPHId filterPName + let ty = parrElemType cea + (clam,_) <- deLambda ty pa b + dePArrComp qs pa (mkApps (Var filterP) [Type ty, clam, cea]) + +-- +-- <<[:e' | p <- e, qs:]>> pa ea = +-- let ef = \pa -> e +-- in +-- <<[:e' | qs:]>> (pa, p) (crossMap ea ef) +-- +-- if matching again p cannot fail, or else -- -- <<[:e' | p <- e, qs:]>> pa ea = -- let ef = \pa -> filterP (\x -> case x of {p -> True; _ -> False}) e -- in -- <<[:e' | qs:]>> (pa, p) (crossMapP ea ef) -- -dePArrComp (BindStmt p e _ _ : qs) body pa cea = - dsLookupGlobalId filterPName `thenDs` \filterP -> - dsLookupGlobalId crossMapPName `thenDs` \crossMapP -> - dsLExpr e `thenDs` \ce -> - let ety'cea = parrElemType cea - ety'ce = parrElemType ce - false = Var falseDataConId - true = Var trueDataConId - in - newSysLocalDs ety'ce `thenDs` \v -> - matchSimply (Var v) (StmtCtxt PArrComp) p true false `thenDs` \pred -> - let cef = mkApps (Var filterP) [Type ety'ce, mkLams [v] pred, ce] - in - mkLambda ety'cea pa cef `thenDs` \(clam, - _ ) -> - let ety'cef = ety'ce -- filter doesn't change the element type - pa' = mkTuplePat [pa, p] - in - dePArrComp qs body pa' (mkApps (Var crossMapP) - [Type ety'cea, Type ety'cef, cea, clam]) +dePArrComp (BindStmt p e _ _ : qs) pa cea = do + filterP <- dsLookupDPHId filterPName + crossMapP <- dsLookupDPHId crossMapPName + ce <- dsLExpr e + let ety'cea = parrElemType cea + ety'ce = parrElemType ce + false = Var falseDataConId + true = Var trueDataConId + v <- newSysLocalDs ety'ce + pred <- matchSimply (Var v) (StmtCtxt PArrComp) p true false + let cef | isIrrefutableHsPat p = ce + | otherwise = mkApps (Var filterP) [Type ety'ce, mkLams [v] pred, ce] + (clam, _) <- mkLambda ety'cea pa cef + let ety'cef = ety'ce -- filter doesn't change the element type + pa' = mkLHsPatTup [pa, p] + + dePArrComp qs pa' (mkApps (Var crossMapP) + [Type ety'cea, Type ety'cef, cea, clam]) -- -- <<[:e' | let ds, qs:]>> pa ea = -- <<[:e' | qs:]>> (pa, (x_1, ..., x_n)) @@ -429,32 +599,29 @@ dePArrComp (BindStmt p e _ _ : qs) body pa cea = -- where -- {x_1, ..., x_n} = DV (ds) -- Defined Variables -- -dePArrComp (LetStmt ds : qs) body pa cea = - dsLookupGlobalId mapPName `thenDs` \mapP -> - let xs = map unLoc (collectLocalBinders ds) - ty'cea = parrElemType cea - in - newSysLocalDs ty'cea `thenDs` \v -> - dsLocalBinds ds (mkCoreTup (map Var xs)) `thenDs` \clet -> - newSysLocalDs (exprType clet) `thenDs` \let'v -> - let projBody = mkDsLet (NonRec let'v clet) $ - mkCoreTup [Var v, Var let'v] - errTy = exprType projBody - errMsg = "DsListComp.dePArrComp: internal error!" - in - mkErrorAppDs pAT_ERROR_ID errTy errMsg `thenDs` \cerr -> - matchSimply (Var v) (StmtCtxt PArrComp) pa projBody cerr`thenDs` \ccase -> - let pa' = mkTuplePat [pa, mkTuplePat (map nlVarPat xs)] - proj = mkLams [v] ccase - in - dePArrComp qs body pa' (mkApps (Var mapP) - [Type ty'cea, Type errTy, proj, cea]) +dePArrComp (LetStmt ds : qs) pa cea = do + mapP <- dsLookupDPHId mapPName + let xs = collectLocalBinders ds + ty'cea = parrElemType cea + v <- newSysLocalDs ty'cea + clet <- dsLocalBinds ds (mkCoreTup (map Var xs)) + let'v <- newSysLocalDs (exprType clet) + let projBody = mkCoreLet (NonRec let'v clet) $ + mkCoreTup [Var v, Var let'v] + errTy = exprType projBody + errMsg = ptext (sLit "DsListComp.dePArrComp: internal error!") + cerr <- mkErrorAppDs pAT_ERROR_ID errTy errMsg + ccase <- matchSimply (Var v) (StmtCtxt PArrComp) pa projBody cerr + let pa' = mkLHsPatTup [pa, mkLHsPatTup (map nlVarPat xs)] + proj = mkLams [v] ccase + 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 = @@ -463,31 +630,28 @@ dePArrComp (ParStmt _ : _) _ _ _ = -- where -- {x_1, ..., x_n} = DV (qs) -- -dePArrParComp qss body = - deParStmt qss `thenDs` \(pQss, - ceQss) -> - dePArrComp [] body pQss ceQss +dePArrParComp :: [([LStmt Id], [Id])] -> [Stmt Id] -> DsM CoreExpr +dePArrParComp qss quals = do + (pQss, ceQss) <- deParStmt qss + 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) = -- first statement - let res_expr = mkExplicitTuple (map nlHsVar xs) - in - dsPArrComp (map unLoc qs) res_expr undefined `thenDs` \cqs -> - parStmts qss (mkTuplePat (map nlVarPat xs)) cqs + deParStmt ((qs, xs):qss) = do -- first statement + let res_expr = mkLHsVarTuple xs + cqs <- dsPArrComp (map unLoc qs ++ [mkLastStmt res_expr]) + parStmts qss (mkLHsVarPatTup xs) cqs --- parStmts [] pa cea = return (pa, cea) - parStmts ((qs, xs):qss) pa cea = -- subsequent statements (zip'ed) - dsLookupGlobalId zipPName `thenDs` \zipP -> - let pa' = mkTuplePat [pa, mkTuplePat (map nlVarPat xs)] - ty'cea = parrElemType cea - res_expr = mkExplicitTuple (map nlHsVar xs) - in - dsPArrComp (map unLoc qs) res_expr undefined `thenDs` \cqs -> + parStmts ((qs, xs):qss) pa cea = do -- subsequent statements (zip'ed) + zipP <- dsLookupDPHId zipPName + let pa' = mkLHsPatTup [pa, mkLHsVarPatTup xs] + ty'cea = parrElemType cea + res_expr = mkLHsVarTuple xs + 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] - in + cea' = mkApps (Var zipP) [Type ty'cea, Type ty'cqs, cea, cqs] parStmts qss pa' cea' -- generate Core corresponding to `\p -> e' @@ -497,8 +661,7 @@ deLambda :: Type -- type of the argument -> LHsExpr Id -- body -> DsM (CoreExpr, Type) deLambda ty p e = - dsLExpr e `thenDs` \ce -> - mkLambda ty p ce + mkLambda ty p =<< dsLExpr e -- generate Core for a lambda pattern match, where the body is already in Core -- @@ -506,14 +669,13 @@ mkLambda :: Type -- type of the argument -> LPat Id -- argument pattern -> CoreExpr -- desugared body -> DsM (CoreExpr, Type) -mkLambda ty p ce = - newSysLocalDs ty `thenDs` \v -> - let errMsg = "DsListComp.deLambda: internal error!" - ce'ty = exprType ce - in - mkErrorAppDs pAT_ERROR_ID ce'ty errMsg `thenDs` \cerr -> - matchSimply (Var v) (StmtCtxt PArrComp) p ce cerr `thenDs` \res -> - returnDs (mkLams [v] res, ce'ty) +mkLambda ty p ce = do + v <- newSysLocalDs ty + let errMsg = ptext (sLit "DsListComp.deLambda: internal error!") + ce'ty = exprType ce + cerr <- mkErrorAppDs pAT_ERROR_ID ce'ty errMsg + res <- matchSimply (Var v) (StmtCtxt PArrComp) p ce cerr + return (mkLams [v] res, ce'ty) -- obtain the element type of the parallel array produced by the given Core -- expression @@ -524,16 +686,243 @@ parrElemType e = Just (tycon, [ty]) | tycon == parrTyCon -> ty _ -> panic "DsListComp.parrElemType: not a parallel array type" +\end{code} + +Translation for monad comprehensions --- Smart constructor for source tuple patterns +\begin{code} +-- Entry point for monad comprehension desugaring +dsMonadComp :: [LStmt Id] -> DsM CoreExpr +dsMonadComp stmts = dsMcStmts stmts + +dsMcStmts :: [LStmt Id] -> DsM CoreExpr +dsMcStmts [] = panic "dsMcStmts" +dsMcStmts (L loc stmt : lstmts) = putSrcSpanDs loc (dsMcStmt stmt lstmts) + +--------------- +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 + = do { rest <- dsMcStmts stmts + ; dsLocalBinds binds rest } + +-- [ .. | a <- m, stmts ] +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 + = do { exp' <- dsLExpr exp + ; guard_exp' <- dsExpr guard_exp + ; then_exp' <- dsExpr then_exp + ; rest <- dsMcStmts stmts + ; return $ mkApps then_exp' [ mkApps guard_exp' [exp'] + , rest ] } + +-- Transform statements desugar like this: +-- +-- [ .. | qs, then f by e ] -> f (\q_v -> e) [| qs |] +-- +-- 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 + = 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 + 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_tup_type) : using_args) + + ; dsMcBindStmt pat rhs bind_op noSyntaxExpr stmts_rest } + +-- Group statements desugar like this: -- -mkTuplePat :: [LPat Id] -> LPat Id -mkTuplePat [lpat] = lpat -mkTuplePat lpats = noLoc $ mkVanillaTuplePat lpats Boxed +-- [| (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) + +dsMcStmt (GroupStmt { grpS_stmts = stmts, grpS_bndrs = bndrs + , grpS_by = by, grpS_using = using + , grpS_ret = return_op, grpS_bind = bind_op + , grpS_fmap = fmap_op }) stmts_rest + = do { let (from_bndrs, to_bndrs) = unzip bndrs + from_bndr_tys = map idType from_bndrs -- Types ty + + -- Desugar an inner comprehension which outputs a list of tuples of the "from" binders + ; expr <- dsInnerMonadComp stmts from_bndrs 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 + ; usingExpr' <- dsLExpr using + ; usingArgs <- case by of + Nothing -> return [expr] + Just by_e -> do { by_e' <- dsLExpr by_e + ; lam <- matchTuple from_bndrs by_e' + ; return [lam, expr] } + + -- Generate the expressions to build the grouped list + -- Build a pattern that ensures the consumer binds into the NEW binders, + -- which hold monads rather than single values + ; fmap_op' <- dsExpr fmap_op + ; 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 -- n (a,b,c) + tup_n_ty = mkBigCoreVarTupTy to_bndrs + + ; body <- dsMcStmts stmts_rest + ; n_tup_var <- newSysLocalDs n_tup_ty + ; tup_n_var <- newSysLocalDs tup_n_ty + ; tup_n_expr <- mkMcUnzipM fmap_op' n_tup_var from_bndr_tys + ; us <- newUniqueSupply + ; let rhs' = mkApps usingExpr' usingArgs + body' = mkTupleCase us to_bndrs body tup_n_var tup_n_expr + + ; 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)) +-- <- [bndrs1 | qs1] `mzip` ([bndrs2 | qs2] `mzip` [bndrs3 | qs3]) ] +-- +-- 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_w_tys <- mapM ds_inner pairs -- Pairs (exp :: m ty, ty) + ; mzip_op' <- dsExpr mzip_op + + ; let -- The pattern variables + pats = map (mkBigLHsVarPatTup . snd) pairs + -- Pattern with tuples of variables + -- [v1,v2,v3] => (v1, (v2, v3)) + pat = foldr1 (\p1 p2 -> mkLHsPatTup [p1, p2]) pats + (rhs, _) = foldr1 (\(e1,t1) (e2,t2) -> + (mkApps mzip_op' [Type t1, Type t2, e1, e2], + mkBoxedTupleTy [t1,t2])) + exps_w_tys + + ; dsMcBindStmt pat rhs bind_op noSyntaxExpr stmts_rest } + where + ds_inner (stmts, bndrs) = do { exp <- dsInnerMonadComp stmts bndrs mono_ret_op + ; return (exp, tup_ty) } + where + mono_ret_op = HsWrap (WpTyApp tup_ty) return_op + tup_ty = mkBigCoreVarTupTy bndrs + +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 (mkBigCoreVarTupTy ids) + ; return (Lam tup_id $ mkTupleCase us ids body tup_id (Var tup_id)) } + +-- general `rhs' >>= \pat -> stmts` desugaring where `rhs'` is already a +-- desugared `CoreExpr` +dsMcBindStmt :: LPat Id + -> CoreExpr -- ^ the desugared rhs of the bind statement + -> SyntaxExpr Id + -> SyntaxExpr Id + -> [LStmt Id] + -> DsM CoreExpr +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 + res1_ty = funResultTy (funArgTy (funResultTy bind_ty)) + ; match <- matchSinglePat (Var var) (StmtCtxt DoExpr) pat + res1_ty (cantFailMatchResult body) + ; match_code <- handle_failure pat match fail_op + ; return (mkApps bind_op' [rhs', Lam var match_code]) } --- Smart constructor for source tuple expressions + where + -- In a monad comprehension expression, pattern-match failure just calls + -- the monadic `fail` rather than throwing an exception + handle_failure pat match fail_op + | matchCanFail match + = do { fail_op' <- dsExpr fail_op + ; fail_msg <- mkStringExpr (mk_fail_msg pat) + ; extractMatchResult match (App fail_op' fail_msg) } + | otherwise + = extractMatchResult match (error "It can't fail") + + mk_fail_msg :: Located e -> String + mk_fail_msg pat = "Pattern match failure in monad comprehension at " ++ + showSDoc (ppr (getLoc pat)) + +-- Desugar nested monad comprehensions, for example in `then..` constructs +-- 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 + -> HsExpr Id -- The monomorphic "return" operator + -> DsM CoreExpr +dsInnerMonadComp stmts bndrs ret_op + = dsMcStmts (stmts ++ [noLoc (LastStmt (mkBigLHsVarTup bndrs) ret_op)]) + +-- The `unzip` function for `GroupStmt` in a monad comprehensions +-- +-- unzip :: m (a,b,..) -> (m a,m b,..) +-- unzip m_tuple = ( liftM selN1 m_tuple +-- , liftM selN2 m_tuple +-- , .. ) -- -mkExplicitTuple :: [LHsExpr id] -> LHsExpr id -mkExplicitTuple [lexp] = lexp -mkExplicitTuple lexps = noLoc $ ExplicitTuple lexps Boxed +-- mkMcUnzipM fmap ys [t1, t2] +-- = ( fmap (selN1 :: (t1, t2) -> t1) ys +-- , fmap (selN2 :: (t1, t2) -> t2) ys ) + +mkMcUnzipM :: CoreExpr -- fmap + -> Id -- Of type n (a,b,c) + -> [Type] -- [a,b,c] + -> DsM CoreExpr -- Of type (n a, n b, n c) +mkMcUnzipM fmap_op ys elt_tys + = do { xs <- mapM newSysLocalDs elt_tys + ; tup_xs <- newSysLocalDs (mkBigCoreTupTy elt_tys) + + ; let arg_ty = idType ys + mk_elt i = mkApps fmap_op -- fmap :: forall a b. (a -> b) -> n a -> n b + [ Type arg_ty, Type (elt_tys !! i) + , mk_sel i, Var ys] + + mk_sel n = Lam tup_xs $ + mkTupleSelector xs (xs !! n) tup_xs (Var tup_xs) + + ; return (mkBigCoreTup (map mk_elt [0..length elt_tys - 1])) } \end{code}