%
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
-\section[DsListComp]{Desugaring list comprehensions}
+\section[DsListComp]{Desugaring list comprehensions and array comprehensions}
\begin{code}
-module DsListComp ( dsListComp ) where
+module DsListComp ( dsListComp, dsPArrComp ) where
#include "HsVersions.h"
import {-# SOURCE #-} DsExpr ( dsExpr, dsLet )
-import HsSyn ( Stmt(..), HsExpr )
-import TcHsSyn ( TypecheckedStmt, TypecheckedHsExpr )
-import DsHsSyn ( outPatType )
+import BasicTypes ( Boxity(..) )
+import TyCon ( tyConName )
+import HsSyn ( Pat(..), HsExpr(..), Stmt(..),
+ HsMatchContext(..), HsStmtContext(..),
+ collectHsBinders )
+import TcHsSyn ( TypecheckedStmt, TypecheckedPat, TypecheckedHsExpr,
+ hsPatType )
import CoreSyn
import DsMonad -- the monadery used in the desugarer
import DsUtils
import CmdLineOpts ( opt_FoldrBuildOn )
-import CoreUtils ( coreExprType )
-import Var ( Id, TyVar )
-import Const ( Con(..) )
-import PrelInfo ( foldrId )
-import Type ( mkTyVarTy, mkForAllTy, mkFunTys, mkFunTy, Type )
-import TysPrim ( alphaTyVar, alphaTy )
-import TysWiredIn ( nilDataCon, consDataCon, listTyCon )
+import CoreUtils ( exprType, mkIfThenElse )
+import Id ( idType )
+import Var ( Id )
+import Type ( mkTyVarTy, mkFunTys, mkFunTy, Type,
+ splitTyConApp_maybe )
+import TysPrim ( alphaTyVar )
+import TysWiredIn ( nilDataCon, consDataCon, trueDataConId, falseDataConId,
+ unitDataConId, unitTy,
+ mkListTy, mkTupleTy )
import Match ( matchSimply )
-import Outputable
+import PrelNames ( foldrName, buildName, replicatePName, mapPName,
+ filterPName, zipPName, crossPName, parrTyConName )
+import PrelInfo ( pAT_ERROR_ID )
+import SrcLoc ( noSrcLoc )
+import Panic ( panic )
\end{code}
List comprehensions may be desugared in one of two ways: ``ordinary''
-> DsM CoreExpr
dsListComp quals elt_ty
- | not opt_FoldrBuildOn -- Be boring
- = deListComp quals nil_expr
+ | not opt_FoldrBuildOn -- Be boring
+ || isParallelComp quals
+ = deListComp quals (mkNilExpr elt_ty)
| otherwise -- foldr/build lives!
= newTyVarsDs [alphaTyVar] `thenDs` \ [n_tyvar] ->
let
- alpha_to_alpha = alphaTy `mkFunTy` alphaTy
-
n_ty = mkTyVarTy n_tyvar
c_ty = mkFunTys [elt_ty, n_ty] n_ty
- g_ty = mkForAllTy alphaTyVar (
- (elt_ty `mkFunTy` alpha_to_alpha)
- `mkFunTy`
- alpha_to_alpha
- )
in
- newSysLocalsDs [c_ty,n_ty,g_ty] `thenDs` \ [c, n, g] ->
-
- dfListComp c_ty c
- n_ty n
- quals `thenDs` \ result ->
-
- returnDs (mkBuild elt_ty n_tyvar c n g result)
- where
- nil_expr = mkNilExpr elt_ty
+ newSysLocalsDs [c_ty,n_ty] `thenDs` \ [c, n] ->
+ dfListComp c n quals `thenDs` \ result ->
+ dsLookupGlobalId buildName `thenDs` \ build_id ->
+ returnDs (Var build_id `App` Type elt_ty
+ `App` mkLams [n_tyvar, c, n] result)
+
+ where isParallelComp (ParStmtOut bndrstmtss : _) = True
+ isParallelComp _ = False
\end{code}
%************************************************************************
is the TE translation scheme. Note that we carry around the @L@ list
already desugared. @dsListComp@ does the top TE rule mentioned above.
-deListComp :: [TypecheckedStmt]
- -> CoreExpr -> CoreExpr -- Cons and nil resp; can be copied freely
- -> DsM CoreExpr
-
-deListComp [ReturnStmt expr] cons nil
- = dsExpr expr `thenDs` \ expr' ->
- returnDs (mkApps cons [expr', nil])
-
-deListComp (GuardStmt guard locn : quals) cons nil
- = dsExpr guard `thenDs` \ guard' ->
- deListComp quals cons nil `thenDs` \ rest' ->
- returnDs (mkIfThenElse guard' rest' nil)
-
-deListComp (LetStmt binds : quals) cons nil
- = deListComp quals cons nil `thenDs` \ rest' ->
- dsLet binds rest'
-
-deListComp (BindStmt pat list locn : quals) cons nil
- = dsExpr list `thenDs` \ list' ->
- let
- pat_ty = outPatType pat
- nil_ty = coreExprType nil
- in
- newSysLocalsDs [pat_ty, nil_ty] `thenDs` \ [x,ys] ->
-
- dsListComp quals cons (Var ys) `thenDs` \ rest ->
- matchSimply (Var x) ListCompMatch pat
- rest (Var ys) `thenDs` \ core_match ->
- bindNonRecDs (mkLams [x,ys] fn_body) $ \ fn ->
- dsListExpr list (Var fn) nil
-
-
-data FExpr = FEOther CoreExpr -- Default case
- | FECons -- cons
- | FEConsComposedWith CoreExpr -- (cons . e)
- | FENil -- nil
-
-feComposeWith FECons g
- = returnDs (FEConsComposedWith g)
-
-feComposeWith (FEOther f) g
- = composeWith f f `thenDs` \ h ->
- returnDs (FEOther h)
-
-feComposeWith (FEConsComposedWith f) g
- = composeWith f f `thenDs` \ h ->
- returnDs (FEConsComposedWith h)
-
-
-composeWith f g
- = newSysLocalDs arg_ty `thenDs` \ x ->
- returnDs (Lam x (App e (App f (Var x))))
- where
- arg_ty = case splitFunTy_maybe (coreExprType g) of
- Just (arg_ty,_) -> arg_ty
- other -> panic "feComposeWith"
-
-deListExpr :: TypecheckedHsExpr
- -> FExpr -> FExpr -- Cons and nil expressions
- -> DsM CoreExpr
-
-deListExpr cons nil (HsDoOut ListComp stmts _ _ _ result_ty src_loc)
- = deListComp stmts cons nil
-
-deListExpr cons nil (HsVar map, _, [f,xs])
- | goodInst var mapIdKey = dsExpr f `thenDs` \ f' ->
- feComposeWith cons f' `thenDs` \ cons' ->
- in
- deListExpr xs cons' nil
-
-
-data HsExprForm = GoodForm What [Type] [TypecheckedHsExpr]
- | BadForm
-
-data What = HsMap | HsConcat | HsFilter | HsZip | HsFoldr
+To the above, we add an additional rule to deal with parallel list
+comprehensions. The translation goes roughly as follows:
+ [ e | p1 <- e11, let v1 = e12, p2 <- e13
+ | q1 <- e21, let v2 = e22, q2 <- e23]
+ =>
+ [ e | ((x1, .., xn), (y1, ..., ym)) <-
+ zip [(x1,..,xn) | p1 <- e11, let v1 = e12, p2 <- e13]
+ [(y1,..,ym) | q1 <- e21, let v2 = e22, q2 <- e23]]
+where (x1, .., xn) are the variables bound in p1, v1, p2
+ (y1, .., ym) are the variables bound in q1, v2, q2
+
+In the translation below, the ParStmtOut branch translates each parallel branch
+into a sub-comprehension, and desugars each independently. The resulting lists
+are fed to a zip function, we create a binding for all the variables bound in all
+the comprehensions, and then we hand things off the the desugarer for bindings.
+The zip function is generated here a) because it's small, and b) because then we
+don't have to deal with arbitrary limits on the number of zip functions in the
+prelude, nor which library the zip function came from.
+The introduced tuples are Boxed, but only because I couldn't get it to work
+with the Unboxed variety.
-analyseListProducer (HsVar v) ty_args val_args
- | good_inst mapIdKey 2 = GoodForm HsMap ty_args val_args
- | good_inst concatIdKey 1 = GoodForm HsConcat ty_args val_args
- | good_inst filterIdKey 2 = GoodForm HsFilter ty_args val_args
- | good_id zipIdKey 2 = GoodForm HsZip ty_args val_args
- | otherwise =
- where
- good_inst key arity = isInstIdOf key v && result_is_list && n_args == arity
- good_id key arity = getUnique v == key && result_is_list && n_args == arity
+\begin{code}
- n_args :: Int
- n_args = length val_args
+deListComp :: [TypecheckedStmt] -> CoreExpr -> DsM CoreExpr
- result_is_list = resultTyIsList (idType v) ty_args val_args
+deListComp (ParStmtOut bndrstmtss : quals) list
+ = mapDs do_list_comp bndrstmtss `thenDs` \ exps ->
+ mkZipBind qual_tys `thenDs` \ (zip_fn, zip_rhs) ->
-resultTyIsList ty ty_args val_args
- = go ty ty_args
- where
- go1 ty (_:tys) = case splitForAllTy_maybe ty of
- Just (_,ty) -> go1 ty tys
- Nothing -> False
- go1 ty [] = go2 ty val_args
+ -- 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
- go2 ty (_:args) = case splitFunTy_maybe of
- Just (_,ty) -> go2 ty args
- Nothing -> False
+ where -- pat is the pattern ((x1,..,xn), (y1,..,ym)) in the example above
+ pat = TuplePat pats Boxed
+ pats = map (\(bs,_) -> mk_hs_tuple_pat bs) bndrstmtss
- go2 ty [] = case splitTyConApp_maybe of
- Just (tycon, [_]) | tycon == listTyCon -> True
- other -> False
+ -- Types of (x1,..,xn), (y1,..,yn) etc
+ qual_tys = [ mk_bndrs_tys bndrs | (bndrs,_) <- bndrstmtss ]
+ do_list_comp (bndrs, stmts)
+ = dsListComp (stmts ++ [ResultStmt (mk_hs_tuple_expr bndrs) noSrcLoc])
+ (mk_bndrs_tys bndrs)
-\begin{code}
-deListComp :: [TypecheckedStmt] -> CoreExpr -> DsM CoreExpr
+ mk_bndrs_tys bndrs = mk_tuple_ty (map idType bndrs)
-deListComp [ReturnStmt expr] list -- Figure 7.4, SLPJ, p 135, rule C above
+ -- Last: the one to return
+deListComp [ResultStmt expr locn] list -- Figure 7.4, SLPJ, p 135, rule C above
= dsExpr expr `thenDs` \ core_expr ->
- returnDs (mkConApp consDataCon [Type (coreExprType core_expr), core_expr, list])
+ returnDs (mkConsExpr (exprType core_expr) core_expr list)
-deListComp (GuardStmt guard locn : quals) list -- rule B above
+ -- Non-last: must be a guard
+deListComp (ExprStmt guard ty locn : quals) list -- rule B above
= dsExpr guard `thenDs` \ core_guard ->
deListComp quals list `thenDs` \ core_rest ->
returnDs (mkIfThenElse core_guard core_rest list)
deListComp (BindStmt pat list1 locn : quals) core_list2 -- rule A' above
= dsExpr list1 `thenDs` \ core_list1 ->
- let
- u3_ty@u1_ty = coreExprType core_list1 -- two names, same thing
+ deBindComp pat core_list1 quals core_list2
+\end{code}
+
+
+\begin{code}
+deBindComp pat core_list1 quals core_list2
+ = let
+ u3_ty@u1_ty = exprType core_list1 -- two names, same thing
-- u1_ty is a [alpha] type, and u2_ty = alpha
- u2_ty = outPatType pat
+ u2_ty = hsPatType pat
- res_ty = coreExprType core_list2
+ 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] ->
letrec_body = App (Var h) core_list1
in
deListComp quals core_fail `thenDs` \ rest_expr ->
- matchSimply (Var u2) ListCompMatch pat
+ matchSimply (Var u2) (StmtCtxt ListComp) pat
rest_expr core_fail `thenDs` \ core_match ->
let
rhs = Lam u1 $
- Case (Var u1) u1 [(DataCon nilDataCon, [], core_list2),
- (DataCon consDataCon, [u2, u3], core_match)]
+ Case (Var u1) u1 [(DataAlt nilDataCon, [], core_list2),
+ (DataAlt consDataCon, [u2, u3], core_match)]
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
+ = mapDs newSysLocalDs list_tys `thenDs` \ ass ->
+ mapDs newSysLocalDs elt_tys `thenDs` \ as' ->
+ mapDs 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 = mk_tuple_ty elt_tys
+ zip_fn_ty = mkFunTys list_tys (mkListTy ret_elt_ty)
+
+ mk_case (as, a', as') rest
+ = Case (Var as) as [(DataAlt nilDataCon, [], mkNilExpr ret_elt_ty),
+ (DataAlt consDataCon, [a', as'], rest)]
+
+-- Helper function
+mk_tuple_ty :: [Type] -> Type
+mk_tuple_ty [ty] = ty
+mk_tuple_ty tys = mkTupleTy Boxed (length tys) tys
+
+-- Helper functions that makes an HsTuple only for non-1-sized tuples
+mk_hs_tuple_expr :: [Id] -> TypecheckedHsExpr
+mk_hs_tuple_expr [] = HsVar unitDataConId
+mk_hs_tuple_expr [id] = HsVar id
+mk_hs_tuple_expr ids = ExplicitTuple [ HsVar i | i <- ids ] Boxed
+
+mk_hs_tuple_pat :: [Id] -> TypecheckedPat
+mk_hs_tuple_pat [b] = VarPat b
+mk_hs_tuple_pat bs = TuplePat (map VarPat bs) Boxed
+\end{code}
+
+
%************************************************************************
%* *
\subsection[DsListComp-foldr-build]{Foldr/Build desugaring of list comprehensions}
%************************************************************************
@dfListComp@ are the rules used with foldr/build turned on:
+
\begin{verbatim}
-TE < [ e | ] >> c n = c e n
-TE << [ e | b , q ] >> c n = if b then TE << [ e | q ] >> c n else n
-TE << [ e | p <- l , q ] c n = foldr
- (\ TE << p >> b -> TE << [ e | q ] >> c b
- _ b -> b) n l
+TE[ e | ] c n = c e n
+TE[ e | b , q ] c n = if b then TE[ e | q ] c n else n
+TE[ e | p <- l , q ] c n = let
+ f = \ x b -> case x of
+ p -> TE[ e | q ] c b
+ _ -> b
+ in
+ foldr f n l
\end{verbatim}
+
\begin{code}
-dfListComp :: Type -> Id -- 'c'; its type and id
- -> Type -> Id -- 'n'; its type and id
+dfListComp :: Id -> Id -- 'c' and 'n'
-> [TypecheckedStmt] -- the rest of the qual's
-> DsM CoreExpr
-dfListComp c_ty c_id n_ty n_id [ReturnStmt expr]
+ -- Last: the one to return
+dfListComp c_id n_id [ResultStmt expr locn]
= dsExpr expr `thenDs` \ core_expr ->
returnDs (mkApps (Var c_id) [core_expr, Var n_id])
-dfListComp c_ty c_id n_ty n_id (GuardStmt guard locn : quals)
+ -- Non-last: must be a guard
+dfListComp c_id n_id (ExprStmt guard ty locn : quals)
= dsExpr guard `thenDs` \ core_guard ->
- dfListComp c_ty c_id n_ty n_id quals `thenDs` \ core_rest ->
+ dfListComp c_id n_id quals `thenDs` \ core_rest ->
returnDs (mkIfThenElse core_guard core_rest (Var n_id))
-dfListComp c_ty c_id n_ty n_id (LetStmt binds : quals)
+dfListComp c_id n_id (LetStmt binds : quals)
-- new in 1.3, local bindings
- = dfListComp c_ty c_id n_ty n_id quals `thenDs` \ core_rest ->
+ = dfListComp c_id n_id quals `thenDs` \ core_rest ->
dsLet binds core_rest
-dfListComp c_ty c_id n_ty n_id (BindStmt pat list1 locn : quals)
+dfListComp c_id n_id (BindStmt pat list1 locn : quals)
-- evaluate the two lists
= dsExpr list1 `thenDs` \ core_list1 ->
-- find the required type
-
- let p_ty = outPatType pat
- b_ty = n_ty -- alias b_ty to n_ty
- fn_ty = mkFunTys [p_ty, b_ty] b_ty
- lst_ty = coreExprType core_list1
+ let x_ty = hsPatType pat
+ b_ty = idType n_id
in
-- create some new local id's
-
- newSysLocalsDs [b_ty,p_ty,fn_ty,lst_ty] `thenDs` \ [b,p,fn,lst] ->
+ newSysLocalsDs [b_ty,x_ty] `thenDs` \ [b,x] ->
-- build rest of the comprehesion
+ dfListComp c_id b quals `thenDs` \ core_rest ->
- dfListComp c_ty c_id b_ty b quals `thenDs` \ core_rest ->
-- build the pattern match
-
- matchSimply (Var p) ListCompMatch pat core_rest (Var b) `thenDs` \ core_expr ->
+ matchSimply (Var x) (StmtCtxt ListComp)
+ pat core_rest (Var b) `thenDs` \ core_expr ->
-- now build the outermost foldr, and return
-
+ dsLookupGlobalId foldrName `thenDs` \ foldr_id ->
returnDs (
- mkLets
- [NonRec fn (mkLams [p, b] core_expr),
- NonRec lst core_list1]
- (mkFoldr p_ty n_ty fn n_id lst)
+ Var foldr_id `App` Type x_ty
+ `App` Type b_ty
+ `App` mkLams [x, b] core_expr
+ `App` Var n_id
+ `App` core_list1
)
\end{code}
+%************************************************************************
+%* *
+\subsection[DsPArrComp]{Desugaring of array comprehensions}
+%* *
+%************************************************************************
-@mkBuild@ is sugar for building a build!
+\begin{code}
-@mkbuild ty tv c n e@ $Rightarrow$ @build ty (/\ tv -> \ c n -> e)@
-@ty@ is the type of the list.
-@tv@ is always a new type variable.
-@c,n@ are Id's for the abstract cons and nil, @g@ for let binding the argument argument.
- c :: a -> b -> b
- n :: b
- v :: (\/ b . (a -> b -> b) -> b -> b) -> [a]
--- \/ a . (\/ b . (a -> b -> b) -> b -> b) -> [a]
-@e@ is the object right inside the @build@
+-- entry point for desugaring a parallel array comprehension
+--
+-- [:e | qss:] = <<[:e | qss:]>> () [:():]
+--
+dsPArrComp :: [TypecheckedStmt]
+ -> Type -- Don't use; called with `undefined' below
+ -> DsM CoreExpr
+dsPArrComp qs _ =
+ dsLookupGlobalId replicatePName `thenDs` \repP ->
+ let unitArray = mkApps (Var repP) [Type unitTy,
+ mkIntExpr 1,
+ mkCoreTup []]
+ in
+ dePArrComp qs (TuplePat [] Boxed) unitArray
-\begin{code}
-mkBuild :: Type
- -> TyVar
- -> Id
- -> Id
- -> Id
- -> CoreExpr -- template
- -> CoreExpr -- template
-
-mkBuild ty tv c n g expr
- = Let (NonRec g (mkLams [tv, c,n] expr))
- (mkApps (Var buildId) [Type ty, Var g])
-
-buildId = error "DsListComp: buildId"
-
-mkFoldr a b f z xs
- = mkApps (mkTyApps (Var foldrId) [a,b]) [Var f, Var z, Var xs]
+-- the work horse
+--
+dePArrComp :: [TypecheckedStmt]
+ -> TypecheckedPat -- the current generator pattern
+ -> CoreExpr -- the current generator expression
+ -> DsM CoreExpr
+--
+-- <<[:e' | :]>> pa ea = mapP (\pa -> e') ea
+--
+dePArrComp [ResultStmt 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]
+--
+-- <<[:e' | b, qs:]>> pa ea = <<[:e' | qs:]>> pa (filterP (\pa -> b) ea)
+--
+dePArrComp (ExprStmt b _ _ : qs) pa cea =
+ dsLookupGlobalId filterPName `thenDs` \filterP ->
+ let ty = parrElemType cea
+ in
+ deLambda ty pa b `thenDs` \(clam,_) ->
+ dePArrComp qs pa (mkApps (Var filterP) [Type ty, clam, cea])
+--
+-- <<[:e' | p <- e, qs:]>> pa ea =
+-- let ef = filterP (\x -> case x of {p -> True; _ -> False}) e
+-- in
+-- <<[:e' | qs:]>> (pa, p) (crossP ea ef)
+--
+dePArrComp (BindStmt p e _ : qs) pa cea =
+ dsLookupGlobalId filterPName `thenDs` \filterP ->
+ dsLookupGlobalId crossPName `thenDs` \crossP ->
+ dsExpr e `thenDs` \ce ->
+ let ty'cea = parrElemType cea
+ ty'ce = parrElemType ce
+ false = Var falseDataConId
+ true = Var trueDataConId
+ in
+ newSysLocalDs ty'ce `thenDs` \v ->
+ matchSimply (Var v) (StmtCtxt PArrComp) p true false `thenDs` \pred ->
+ let cef = mkApps (Var filterP) [Type ty'ce, mkLams [v] pred, ce]
+ ty'cef = ty'ce -- filterP preserves the type
+ pa' = TuplePat [pa, p] Boxed
+ in
+ dePArrComp qs pa' (mkApps (Var crossP) [Type ty'cea, Type ty'cef, cea, cef])
+--
+-- <<[:e' | let ds, qs:]>> pa ea =
+-- <<[:e' | qs:]>> (pa, (x_1, ..., x_n))
+-- (mapP (\v@pa -> (v, let ds in (x_1, ..., x_n))) ea)
+-- where
+-- {x_1, ..., x_n} = DV (ds) -- Defined Variables
+--
+dePArrComp (LetStmt ds : qs) pa cea =
+ dsLookupGlobalId mapPName `thenDs` \mapP ->
+ let xs = collectHsBinders ds
+ ty'cea = parrElemType cea
+ in
+ newSysLocalDs ty'cea `thenDs` \v ->
+ dsLet 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' = TuplePat [pa, TuplePat (map VarPat xs) Boxed] Boxed
+ proj = mkLams [v] ccase
+ in
+ dePArrComp qs pa' (mkApps (Var mapP) [Type ty'cea, proj, cea])
+--
+-- <<[:e' | qs | qss:]>> pa ea =
+-- <<[:e' | qss:]>> (pa, (x_1, ..., x_n))
+-- (zipP ea <<[:(x_1, ..., x_n) | qs:]>>)
+-- where
+-- {x_1, ..., x_n} = DV (qs)
+--
+dePArrComp (ParStmtOut [] : qss2) pa cea = dePArrComp qss2 pa cea
+dePArrComp (ParStmtOut ((xs, qs):qss) : qss2) pa cea =
+ dsLookupGlobalId zipPName `thenDs` \zipP ->
+ let pa' = TuplePat [pa, TuplePat (map VarPat xs) Boxed] Boxed
+ ty'cea = parrElemType cea
+ resStmt = ResultStmt (ExplicitTuple (map HsVar xs) Boxed) noSrcLoc
+ in
+ dsPArrComp (qs ++ [resStmt]) undefined `thenDs` \cqs ->
+ let ty'cqs = parrElemType cqs
+ cea' = mkApps (Var zipP) [Type ty'cea, Type ty'cqs, cea, cqs]
+ in
+ dePArrComp (ParStmtOut qss : qss2) pa' cea'
+
+-- generate Core corresponding to `\p -> e'
+--
+deLambda :: Type -- type of the argument
+ -> TypecheckedPat -- argument pattern
+ -> TypecheckedHsExpr -- body
+ -> DsM (CoreExpr, Type)
+deLambda ty p e =
+ newSysLocalDs ty `thenDs` \v ->
+ dsExpr e `thenDs` \ce ->
+ let errTy = exprType ce
+ errMsg = "DsListComp.deLambda: internal error!"
+ in
+ mkErrorAppDs pAT_ERROR_ID errTy errMsg `thenDs` \cerr ->
+ matchSimply (Var v) (StmtCtxt PArrComp) p ce cerr `thenDs` \res ->
+ returnDs (mkLams [v] res, errTy)
+
+-- obtain the element type of the parallel array produced by the given Core
+-- expression
+--
+parrElemType :: CoreExpr -> Type
+parrElemType e =
+ case splitTyConApp_maybe (exprType e) of
+ Just (tycon, [ty]) | tyConName tycon == parrTyConName -> ty
+ _ -> panic
+ "DsListComp.parrElemType: not a parallel array type"
\end{code}
-
projects / ghc-hetmet.git / blobdiff