%
% (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 BasicTypes ( Boxity(..) )
-import HsSyn ( OutPat(..), HsExpr(..), Stmt(..), HsMatchContext(..), HsDoContext(..) )
-import TcHsSyn ( TypecheckedStmt, TypecheckedPat, TypecheckedHsExpr )
-import DsHsSyn ( outPatType )
+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 CoreUtils ( exprType, mkIfThenElse )
import Id ( idType )
import Var ( Id )
-import Type ( mkTyVarTy, mkFunTys, mkFunTy, Type )
+import Type ( mkTyVarTy, mkFunTys, mkFunTy, Type,
+ splitTyConApp_maybe )
import TysPrim ( alphaTyVar )
-import TysWiredIn ( nilDataCon, consDataCon, unitDataConId, mkListTy, mkTupleTy )
+import TysWiredIn ( nilDataCon, consDataCon, trueDataConId, falseDataConId,
+ unitDataConId, unitTy,
+ mkListTy, mkTupleTy )
import Match ( matchSimply )
-import PrelNames ( foldrName, buildName )
+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''
in
newSysLocalsDs [c_ty,n_ty] `thenDs` \ [c, n] ->
dfListComp c n quals `thenDs` \ result ->
- dsLookupGlobalValue buildName `thenDs` \ build_id ->
+ dsLookupGlobalId buildName `thenDs` \ build_id ->
returnDs (Var build_id `App` Type elt_ty
`App` mkLams [n_tyvar, c, n] result)
returnDs (mkConsExpr (exprType core_expr) core_expr list)
-- Non-last: must be a guard
-deListComp (ExprStmt guard locn : quals) list -- rule B above
+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)
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 = exprType core_list2
h_ty = u1_ty `mkFunTy` res_ty
letrec_body = App (Var h) core_list1
in
deListComp quals core_fail `thenDs` \ rest_expr ->
- matchSimply (Var u2) (DoCtxt ListComp) pat
+ matchSimply (Var u2) (StmtCtxt ListComp) pat
rest_expr core_fail `thenDs` \ core_match ->
let
rhs = Lam u1 $
mapDs newSysLocalDs list_tys `thenDs` \ as's ->
newSysLocalDs zip_fn_ty `thenDs` \ zip_fn ->
let
- inner_rhs = mkConsExpr ret_elt_ty (mkTupleExpr as') (mkVarApps (Var zip_fn) as's)
+ 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)
returnDs (mkApps (Var c_id) [core_expr, Var n_id])
-- Non-last: must be a guard
-dfListComp c_id n_id (ExprStmt guard locn : quals)
+dfListComp c_id n_id (ExprStmt guard ty locn : quals)
= dsExpr guard `thenDs` \ core_guard ->
dfListComp c_id n_id quals `thenDs` \ core_rest ->
returnDs (mkIfThenElse core_guard core_rest (Var n_id))
= dsExpr list1 `thenDs` \ core_list1 ->
-- find the required type
- let x_ty = outPatType pat
+ let x_ty = hsPatType pat
b_ty = idType n_id
in
dfListComp c_id b quals `thenDs` \ core_rest ->
-- build the pattern match
- matchSimply (Var x) (DoCtxt ListComp)
+ matchSimply (Var x) (StmtCtxt ListComp)
pat core_rest (Var b) `thenDs` \ core_expr ->
-- now build the outermost foldr, and return
- dsLookupGlobalValue foldrName `thenDs` \ foldr_id ->
+ dsLookupGlobalId foldrName `thenDs` \ foldr_id ->
returnDs (
Var foldr_id `App` Type x_ty
`App` Type b_ty
)
\end{code}
+%************************************************************************
+%* *
+\subsection[DsPArrComp]{Desugaring of array comprehensions}
+%* *
+%************************************************************************
+
+\begin{code}
+
+-- 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
+-- 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}