\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 = 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;
-- 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
-- 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 (mkBigLHsVarTup bndrs) bndrs_tuple_type
- return (expr, bndrs_tuple_type)
- where
- bndrs_types = map idType bndrs
- bndrs_tuple_type = mkBigCoreTupTy bndrs_types
-
+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
-- 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 stmts binderMap by using _ _ _) = do
+dsGroupStmt (GroupStmt { grpS_stmts = stmts, grpS_bndrs = binderMap
+ , grpS_by = by, grpS_using = using }) = do
let (fromBinders, toBinders) = unzip binderMap
fromBindersTypes = map idType 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 (either id noLoc using)
+ usingExpr' <- dsLExpr using
usingArgs <- case by of
Nothing -> return [expr]
Just by_e -> do { by_e' <- dsLExpr by_e
\begin{code}
-deListComp :: [Stmt Id] -> LHsExpr Id -> CoreExpr -> DsM CoreExpr
+deListComp :: [Stmt Id] -> CoreExpr -> DsM CoreExpr
+
+deListComp [] _ = panic "deListComp"
+
+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) 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
-- 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
-- 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}
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
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
\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
[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)
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}
%************************************************************************
-- [: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:
--
-- <<[: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
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 =
-- 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
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 =
-- 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
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 =
-- 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)
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'
Translation for monad comprehensions
\begin{code}
-
--- | Keep the "context" of a monad comprehension in a small data type to avoid
--- some boilerplate...
-data DsMonadComp = DsMonadComp
- { mc_return :: Either (SyntaxExpr Id) (Expr CoreBndr)
- , mc_body :: LHsExpr Id
- , mc_m_ty :: Type
- }
-
---
-- 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
- = dsMcStmts stmts (DsMonadComp (Left return_op) body m_ty)
- where
- (m_ty, _) = tcSplitAppTy res_ty
-
-
-dsMcStmts :: [LStmt Id]
- -> DsMonadComp
- -> DsM CoreExpr
+dsMonadComp :: [LStmt Id] -> DsM CoreExpr
+dsMonadComp stmts = dsMcStmts stmts
--- No statements left for desugaring. Desugar the body after calling "return"
--- on it.
-dsMcStmts [] DsMonadComp { mc_return, mc_body }
- = case mc_return of
- Left ret -> dsLExpr $ noLoc ret `nlHsApp` mc_body
- Right ret' -> do
- { body' <- dsLExpr mc_body
- ; return $ mkApps ret' [body'] }
+dsMcStmts :: [LStmt Id] -> DsM CoreExpr
+dsMcStmts [] = panic "dsMcStmts"
+dsMcStmts (L loc stmt : lstmts) = putSrcSpanDs loc (dsMcStmt stmt lstmts)
--- Otherwise desugar each statement step by step
-dsMcStmts ((L loc stmt) : lstmts) mc
- = putSrcSpanDs loc (dsMcStmt stmt lstmts mc)
+---------------
+dsMcStmt :: Stmt Id -> [LStmt Id] -> DsM CoreExpr
-
-dsMcStmt :: Stmt Id
- -> [LStmt Id]
- -> DsMonadComp
- -> 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 ] }
--
-- 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 |] -> (f (\q_v -> e) [| q |]) >>= (return . (unzip q_v))
---
--- which is equal to
---
--- [| q, then group by e using f |] -> liftM (unzip q_v) (f (\q_v -> e) [| q |])
---
--- 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
--- , .. )
--- 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
- = do { let (fromBinders, toBinders) = unzip binderMap
- fromBindersTypes = map idType fromBinders
- fromBindersTupleTy = mkBigCoreTupTy fromBindersTypes
- toBindersTypes = map idType toBinders
- toBindersTupleTy = mkBigCoreTupTy toBindersTypes
- m_ty = mc_m_ty mc
+-- [| (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, fromBinders) (mc { mc_return = Left return_op })
+ ; 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 (either id noLoc using)
+ ; usingExpr' <- dsLExpr using
; 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] }
-
- -- 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
+ ; lam <- matchTuple from_bndrs by_e'
+ ; return [lam, expr] }
-- 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
+ ; 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)) <- 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
- ; mzip_op' <- dsExpr mzip_op
- ; (zip_fn, zip_rhs) <- mkMcZipM mzip_op' (mc_m_ty mc) qual_tys
+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
- vars = map (mkBigLHsVarPatTup . snd) pairs
+ pats = map (mkBigLHsVarPatTup . snd) pairs
-- Pattern with tuples of variables
-- [v1,v2,v3] => (v1, (v2, v3))
- pat = foldr (\tn tm -> mkBigLHsPatTup [tn, tm]) (last vars) (init vars)
- rhs = Let (Rec [(zip_fn, zip_rhs)]) (mkApps (Var zip_fn) exps)
+ 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
- ; dsMcBindStmt pat rhs bind_op noSyntaxExpr stmts_rest mc }
+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 (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`
-> 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
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
+ -> 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
--
-- , liftM selN2 m_tuple
-- , .. )
--
--- mkMcUnzipM m [t1, t2]
--- = (unzip_fn, \ys :: m (t1, t2) ->
--- ( liftM (selN1 :: (t1, t2) -> t1) ys
--- , liftM (selN2 :: (t1, t2) -> t2) ys
--- ))
---
-mkMcUnzipM :: CoreExpr
- -> Type -- m
- -> [Type] -- [a,b,c,..]
- -> DsM (Id, CoreExpr)
-mkMcUnzipM liftM_op m_ty elt_tys
- = do { ys <- newSysLocalDs monad_tuple_ty
- ; xs <- mapM newSysLocalDs elt_tys
- ; scrut <- newSysLocalDs tuple_tys
-
- ; unzip_fn <- newSysLocalDs unzip_fn_ty
-
- ; let -- Select one Id from our tuple
- selectExpr n = mkLams [scrut] $ mkTupleSelector xs (xs !! n) scrut (Var scrut)
- -- Apply 'selectVar' and 'ys' to 'liftM'
- tupleElem n = mkApps liftM_op
- -- Types (m is figured out by the type checker):
- -- liftM :: forall a b. (a -> b) -> m a -> m b
- [ Type tuple_tys, Type (elt_tys !! n)
- -- Arguments:
- , selectExpr n, Var ys ]
- -- The final expression with the big tuple
- unzip_body = mkBigCoreTup [ tupleElem n | n <- [0..length elt_tys - 1] ]
-
- ; return (unzip_fn, mkLams [ys] unzip_body) }
- where monad_tys = map (m_ty `mkAppTy`) elt_tys -- [m a,m b,m c,..]
- tuple_monad_tys = mkBigCoreTupTy monad_tys -- (m a,m b,m c,..)
- tuple_tys = mkBigCoreTupTy elt_tys -- (a,b,c,..)
- monad_tuple_ty = m_ty `mkAppTy` tuple_tys -- m (a,b,c,..)
- unzip_fn_ty = monad_tuple_ty `mkFunTy` tuple_monad_tys -- m (a,b,c,..) -> (m a,m b,m c,..)
-
--- Generate the `mzip` function for `ParStmt` in monad comprehensions, for
--- example:
---
--- mzip :: m t1
--- -> (m t2 -> m t3 -> m (t2, t3))
--- -> m (t1, (t2, t3))
---
--- mkMcZipM m [t1, t2, t3]
--- = (zip_fn, \(q1::t1) (q2::t2) (q3::t3) ->
--- mzip q1 (mzip q2 q3))
---
-mkMcZipM :: CoreExpr
- -> Type
- -> [Type]
- -> DsM (Id, CoreExpr)
-
-mkMcZipM mzip_op m_ty tys@(_:_:_) -- min. 2 types
- = do { (ids, t1, tuple_ty, zip_body) <- loop tys
- ; zip_fn <- newSysLocalDs $
- (m_ty `mkAppTy` t1)
- `mkFunTy`
- (m_ty `mkAppTy` tuple_ty)
- `mkFunTy`
- (m_ty `mkAppTy` mkBigCoreTupTy [t1, tuple_ty])
- ; return (zip_fn, mkLams ids zip_body) }
-
- where
- -- loop :: [Type] -> DsM ([Id], Type, [Type], CoreExpr)
- loop [t1, t2] = do -- last run of the `loop`
- { ids@[a,b] <- newSysLocalsDs (map (m_ty `mkAppTy`) [t1,t2])
- ; let zip_body = mkApps mzip_op [ Type t1, Type t2 , Var a, Var b ]
- ; return (ids, t1, t2, zip_body) }
-
- loop (t1:tr) = do
- { -- Get ty, ids etc from the "inner" zip
- (ids', t1', t2', zip_body') <- loop tr
-
- ; a <- newSysLocalDs $ m_ty `mkAppTy` t1
- ; let tuple_ty' = mkBigCoreTupTy [t1', t2']
- zip_body = mkApps mzip_op [ Type t1, Type tuple_ty', Var a, zip_body' ]
- ; return ((a:ids'), t1, tuple_ty', zip_body) }
-
--- This case should never happen:
-mkMcZipM _ _ tys = pprPanic "mkMcZipM: unexpected argument" (ppr tys)
+-- 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}
projects / ghc-hetmet.git / blobdiff