2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 Desugaring arrow commands
9 module DsArrows ( dsProcExpr ) where
11 #include "HsVersions.h"
17 import HsSyn hiding (collectPatBinders, collectLocatedPatBinders, collectl,
18 collectPatsBinders, collectLocatedPatsBinders)
21 -- NB: The desugarer, which straddles the source and Core worlds, sometimes
22 -- needs to see source types (newtypes etc), and sometimes not
23 -- So WATCH OUT; check each use of split*Ty functions.
24 -- Sigh. This is a pain.
26 import {-# SOURCE #-} DsExpr ( dsExpr, dsLExpr, dsLocalBinds )
51 data DsCmdEnv = DsCmdEnv {
52 meth_binds :: [CoreBind],
53 arr_id, compose_id, first_id, app_id, choice_id, loop_id :: CoreExpr
56 mkCmdEnv :: SyntaxTable Id -> DsM DsCmdEnv
58 (meth_binds, ds_meths) <- dsSyntaxTable ids
60 meth_binds = meth_binds,
61 arr_id = Var (lookupEvidence ds_meths arrAName),
62 compose_id = Var (lookupEvidence ds_meths composeAName),
63 first_id = Var (lookupEvidence ds_meths firstAName),
64 app_id = Var (lookupEvidence ds_meths appAName),
65 choice_id = Var (lookupEvidence ds_meths choiceAName),
66 loop_id = Var (lookupEvidence ds_meths loopAName)
69 bindCmdEnv :: DsCmdEnv -> CoreExpr -> CoreExpr
70 bindCmdEnv ids body = foldr Let body (meth_binds ids)
72 -- arr :: forall b c. (b -> c) -> a b c
73 do_arr :: DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
74 do_arr ids b_ty c_ty f = mkApps (arr_id ids) [Type b_ty, Type c_ty, f]
76 -- (>>>) :: forall b c d. a b c -> a c d -> a b d
77 do_compose :: DsCmdEnv -> Type -> Type -> Type ->
78 CoreExpr -> CoreExpr -> CoreExpr
79 do_compose ids b_ty c_ty d_ty f g
80 = mkApps (compose_id ids) [Type b_ty, Type c_ty, Type d_ty, f, g]
82 -- first :: forall b c d. a b c -> a (b,d) (c,d)
83 do_first :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
84 do_first ids b_ty c_ty d_ty f
85 = mkApps (first_id ids) [Type b_ty, Type c_ty, Type d_ty, f]
87 -- app :: forall b c. a (a b c, b) c
88 do_app :: DsCmdEnv -> Type -> Type -> CoreExpr
89 do_app ids b_ty c_ty = mkApps (app_id ids) [Type b_ty, Type c_ty]
91 -- (|||) :: forall b d c. a b d -> a c d -> a (Either b c) d
92 -- note the swapping of d and c
93 do_choice :: DsCmdEnv -> Type -> Type -> Type ->
94 CoreExpr -> CoreExpr -> CoreExpr
95 do_choice ids b_ty c_ty d_ty f g
96 = mkApps (choice_id ids) [Type b_ty, Type d_ty, Type c_ty, f, g]
98 -- loop :: forall b d c. a (b,d) (c,d) -> a b c
99 -- note the swapping of d and c
100 do_loop :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
101 do_loop ids b_ty c_ty d_ty f
102 = mkApps (loop_id ids) [Type b_ty, Type d_ty, Type c_ty, f]
104 -- map_arrow (f :: b -> c) (g :: a c d) = arr f >>> g :: a b d
105 do_map_arrow :: DsCmdEnv -> Type -> Type -> Type ->
106 CoreExpr -> CoreExpr -> CoreExpr
107 do_map_arrow ids b_ty c_ty d_ty f c
108 = do_compose ids b_ty c_ty d_ty (do_arr ids b_ty c_ty f) c
110 mkFailExpr :: HsMatchContext Id -> Type -> DsM CoreExpr
112 = mkErrorAppDs pAT_ERROR_ID ty (matchContextErrString ctxt)
114 -- construct CoreExpr for \ (a :: a_ty, b :: b_ty) -> b
115 mkSndExpr :: Type -> Type -> DsM CoreExpr
116 mkSndExpr a_ty b_ty = do
117 a_var <- newSysLocalDs a_ty
118 b_var <- newSysLocalDs b_ty
119 pair_var <- newSysLocalDs (mkCorePairTy a_ty b_ty)
121 (coreCasePair pair_var a_var b_var (Var b_var)))
124 Build case analysis of a tuple. This cannot be done in the DsM monad,
125 because the list of variables is typically not yet defined.
128 -- coreCaseTuple [u1..] v [x1..xn] body
129 -- = case v of v { (x1, .., xn) -> body }
130 -- But the matching may be nested if the tuple is very big
132 coreCaseTuple :: UniqSupply -> Id -> [Id] -> CoreExpr -> CoreExpr
133 coreCaseTuple uniqs scrut_var vars body
134 = mkTupleCase uniqs vars body scrut_var (Var scrut_var)
136 coreCasePair :: Id -> Id -> Id -> CoreExpr -> CoreExpr
137 coreCasePair scrut_var var1 var2 body
138 = Case (Var scrut_var) scrut_var (exprType body)
139 [(DataAlt (tupleCon Boxed 2), [var1, var2], body)]
143 mkCorePairTy :: Type -> Type -> Type
144 mkCorePairTy t1 t2 = mkCoreTupTy [t1, t2]
146 mkCorePairExpr :: CoreExpr -> CoreExpr -> CoreExpr
147 mkCorePairExpr e1 e2 = mkCoreTup [e1, e2]
150 The input is divided into a local environment, which is a flat tuple
151 (unless it's too big), and a stack, each element of which is paired
152 with the stack in turn. In general, the input has the form
154 (...((x1,...,xn),s1),...sk)
156 where xi are the environment values, and si the ones on the stack,
157 with s1 being the "top", the first one to be matched with a lambda.
160 envStackType :: [Id] -> [Type] -> Type
161 envStackType ids stack_tys = foldl mkCorePairTy (mkBigCoreVarTupTy ids) stack_tys
163 ----------------------------------------------
166 -- (...((x1,...,xn),s1),...sk)
168 buildEnvStack :: [Id] -> [Id] -> CoreExpr
169 buildEnvStack env_ids stack_ids
170 = foldl mkCorePairExpr (mkBigCoreVarTup env_ids) (map Var stack_ids)
172 ----------------------------------------------
175 -- \ (...((x1,...,xn),s1),...sk) -> e
178 -- case zk of (zk-1,sk) ->
180 -- case z1 of (z0,s1) ->
181 -- case z0 of (x1,...,xn) ->
184 matchEnvStack :: [Id] -- x1..xn
188 matchEnvStack env_ids stack_ids body = do
189 uniqs <- newUniqueSupply
190 tup_var <- newSysLocalDs (mkBigCoreVarTupTy env_ids)
191 matchVarStack tup_var stack_ids
192 (coreCaseTuple uniqs tup_var env_ids body)
195 ----------------------------------------------
198 -- \ (...(z0,s1),...sk) -> e
201 -- case zk of (zk-1,sk) ->
203 -- case z1 of (z0,s1) ->
206 matchVarStack :: Id -- z0
210 matchVarStack env_id [] body
211 = return (Lam env_id body)
212 matchVarStack env_id (stack_id:stack_ids) body = do
213 pair_id <- newSysLocalDs (mkCorePairTy (idType env_id) (idType stack_id))
214 matchVarStack pair_id stack_ids
215 (coreCasePair pair_id env_id stack_id body)
219 mkHsTupleExpr :: [HsExpr Id] -> HsExpr Id
220 mkHsTupleExpr [e] = e
221 mkHsTupleExpr es = ExplicitTuple (map noLoc es) Boxed
223 mkHsPairExpr :: HsExpr Id -> HsExpr Id -> HsExpr Id
224 mkHsPairExpr e1 e2 = mkHsTupleExpr [e1, e2]
226 mkHsEnvStackExpr :: [Id] -> [Id] -> HsExpr Id
227 mkHsEnvStackExpr env_ids stack_ids
228 = foldl mkHsPairExpr (mkHsTupleExpr (map HsVar env_ids)) (map HsVar stack_ids)
231 Translation of arrow abstraction
235 -- A | xs |- c :: [] t' ---> c'
236 -- --------------------------
237 -- A |- proc p -> c :: a t t' ---> arr (\ p -> (xs)) >>> c'
239 -- where (xs) is the tuple of variables bound by p
245 dsProcExpr pat (L _ (HsCmdTop cmd [] cmd_ty ids)) = do
246 meth_ids <- mkCmdEnv ids
247 let locals = mkVarSet (collectPatBinders pat)
248 (core_cmd, _free_vars, env_ids) <- dsfixCmd meth_ids locals [] cmd_ty cmd
249 let env_ty = mkBigCoreVarTupTy env_ids
250 fail_expr <- mkFailExpr ProcExpr env_ty
251 var <- selectSimpleMatchVarL pat
252 match_code <- matchSimply (Var var) ProcExpr pat (mkBigCoreVarTup env_ids) fail_expr
253 let pat_ty = hsLPatType pat
254 proc_code = do_map_arrow meth_ids pat_ty env_ty cmd_ty
257 return (bindCmdEnv meth_ids proc_code)
258 dsProcExpr _ c = pprPanic "dsProcExpr" (ppr c)
261 Translation of command judgements of the form
263 A | xs |- c :: [ts] t
266 dsLCmd :: DsCmdEnv -> IdSet -> [Id] -> [Type] -> Type -> LHsCmd Id
267 -> DsM (CoreExpr, IdSet)
268 dsLCmd ids local_vars env_ids stack res_ty cmd
269 = dsCmd ids local_vars env_ids stack res_ty (unLoc cmd)
271 dsCmd :: DsCmdEnv -- arrow combinators
272 -> IdSet -- set of local vars available to this command
273 -> [Id] -- list of vars in the input to this command
274 -- This is typically fed back,
275 -- so don't pull on it too early
276 -> [Type] -- type of the stack
277 -> Type -- return type of the command
278 -> HsCmd Id -- command to desugar
279 -> DsM (CoreExpr, -- desugared expression
280 IdSet) -- set of local vars that occur free
282 -- A |- f :: a (t*ts) t'
284 -- -----------------------------
285 -- A | xs |- f -< arg :: [ts] t'
287 -- ---> arr (\ ((xs)*ts) -> (arg*ts)) >>> f
289 dsCmd ids local_vars env_ids stack res_ty
290 (HsArrApp arrow arg arrow_ty HsFirstOrderApp _)= do
292 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
293 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
294 core_arrow <- dsLExpr arrow
295 core_arg <- dsLExpr arg
296 stack_ids <- mapM newSysLocalDs stack
297 core_make_arg <- matchEnvStack env_ids stack_ids
298 (foldl mkCorePairExpr core_arg (map Var stack_ids))
299 return (do_map_arrow ids
300 (envStackType env_ids stack)
305 exprFreeVars core_arg `intersectVarSet` local_vars)
307 -- A, xs |- f :: a (t*ts) t'
309 -- ------------------------------
310 -- A | xs |- f -<< arg :: [ts] t'
312 -- ---> arr (\ ((xs)*ts) -> (f,(arg*ts))) >>> app
314 dsCmd ids local_vars env_ids stack res_ty
315 (HsArrApp arrow arg arrow_ty HsHigherOrderApp _) = do
317 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
318 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
320 core_arrow <- dsLExpr arrow
321 core_arg <- dsLExpr arg
322 stack_ids <- mapM newSysLocalDs stack
323 core_make_pair <- matchEnvStack env_ids stack_ids
324 (mkCorePairExpr core_arrow
325 (foldl mkCorePairExpr core_arg (map Var stack_ids)))
327 return (do_map_arrow ids
328 (envStackType env_ids stack)
329 (mkCorePairTy arrow_ty arg_ty)
332 (do_app ids arg_ty res_ty),
333 (exprFreeVars core_arrow `unionVarSet` exprFreeVars core_arg)
334 `intersectVarSet` local_vars)
336 -- A | ys |- c :: [t:ts] t'
338 -- ------------------------
339 -- A | xs |- c e :: [ts] t'
341 -- ---> arr (\ ((xs)*ts) -> let z = e in (((ys),z)*ts)) >>> c
343 dsCmd ids local_vars env_ids stack res_ty (HsApp cmd arg) = do
344 core_arg <- dsLExpr arg
346 arg_ty = exprType core_arg
347 stack' = arg_ty:stack
348 (core_cmd, free_vars, env_ids')
349 <- dsfixCmd ids local_vars stack' res_ty cmd
350 stack_ids <- mapM newSysLocalDs stack
351 arg_id <- newSysLocalDs arg_ty
352 -- push the argument expression onto the stack
354 core_body = bindNonRec arg_id core_arg
355 (buildEnvStack env_ids' (arg_id:stack_ids))
356 -- match the environment and stack against the input
357 core_map <- matchEnvStack env_ids stack_ids core_body
358 return (do_map_arrow ids
359 (envStackType env_ids stack)
360 (envStackType env_ids' stack')
364 (exprFreeVars core_arg `intersectVarSet` local_vars)
365 `unionVarSet` free_vars)
367 -- A | ys |- c :: [ts] t'
368 -- -----------------------------------------------
369 -- A | xs |- \ p1 ... pk -> c :: [t1:...:tk:ts] t'
371 -- ---> arr (\ ((((xs), p1), ... pk)*ts) -> ((ys)*ts)) >>> c
373 dsCmd ids local_vars env_ids stack res_ty
374 (HsLam (MatchGroup [L _ (Match pats _ (GRHSs [L _ (GRHS [] body)] _ ))] _)) = do
376 pat_vars = mkVarSet (collectPatsBinders pats)
377 local_vars' = local_vars `unionVarSet` pat_vars
378 stack' = drop (length pats) stack
379 (core_body, free_vars, env_ids') <- dsfixCmd ids local_vars' stack' res_ty body
380 stack_ids <- mapM newSysLocalDs stack
382 -- the expression is built from the inside out, so the actions
383 -- are presented in reverse order
386 (actual_ids, stack_ids') = splitAt (length pats) stack_ids
387 -- build a new environment, plus what's left of the stack
388 core_expr = buildEnvStack env_ids' stack_ids'
389 in_ty = envStackType env_ids stack
390 in_ty' = envStackType env_ids' stack'
392 fail_expr <- mkFailExpr LambdaExpr in_ty'
393 -- match the patterns against the top of the old stack
394 match_code <- matchSimplys (map Var actual_ids) LambdaExpr pats core_expr fail_expr
395 -- match the old environment and stack against the input
396 select_code <- matchEnvStack env_ids stack_ids match_code
397 return (do_map_arrow ids in_ty in_ty' res_ty select_code core_body,
398 free_vars `minusVarSet` pat_vars)
400 dsCmd ids local_vars env_ids stack res_ty (HsPar cmd)
401 = dsLCmd ids local_vars env_ids stack res_ty cmd
403 -- A, xs |- e :: Bool
404 -- A | xs1 |- c1 :: [ts] t
405 -- A | xs2 |- c2 :: [ts] t
406 -- ----------------------------------------
407 -- A | xs |- if e then c1 else c2 :: [ts] t
409 -- ---> arr (\ ((xs)*ts) ->
410 -- if e then Left ((xs1)*ts) else Right ((xs2)*ts)) >>>
413 dsCmd ids local_vars env_ids stack res_ty (HsIf cond then_cmd else_cmd) = do
414 core_cond <- dsLExpr cond
415 (core_then, fvs_then, then_ids) <- dsfixCmd ids local_vars stack res_ty then_cmd
416 (core_else, fvs_else, else_ids) <- dsfixCmd ids local_vars stack res_ty else_cmd
417 stack_ids <- mapM newSysLocalDs stack
418 either_con <- dsLookupTyCon eitherTyConName
419 left_con <- dsLookupDataCon leftDataConName
420 right_con <- dsLookupDataCon rightDataConName
422 left_expr ty1 ty2 e = mkConApp left_con [Type ty1, Type ty2, e]
423 right_expr ty1 ty2 e = mkConApp right_con [Type ty1, Type ty2, e]
425 in_ty = envStackType env_ids stack
426 then_ty = envStackType then_ids stack
427 else_ty = envStackType else_ids stack
428 sum_ty = mkTyConApp either_con [then_ty, else_ty]
429 fvs_cond = exprFreeVars core_cond `intersectVarSet` local_vars
431 core_if <- matchEnvStack env_ids stack_ids
432 (mkIfThenElse core_cond
433 (left_expr then_ty else_ty (buildEnvStack then_ids stack_ids))
434 (right_expr then_ty else_ty (buildEnvStack else_ids stack_ids)))
435 return (do_map_arrow ids in_ty sum_ty res_ty
437 (do_choice ids then_ty else_ty res_ty core_then core_else),
438 fvs_cond `unionVarSet` fvs_then `unionVarSet` fvs_else)
441 Case commands are treated in much the same way as if commands
442 (see above) except that there are more alternatives. For example
444 case e of { p1 -> c1; p2 -> c2; p3 -> c3 }
448 arr (\ ((xs)*ts) -> case e of
449 p1 -> (Left (Left (xs1)*ts))
450 p2 -> Left ((Right (xs2)*ts))
451 p3 -> Right ((xs3)*ts)) >>>
454 The idea is to extract the commands from the case, build a balanced tree
455 of choices, and replace the commands with expressions that build tagged
456 tuples, obtaining a case expression that can be desugared normally.
457 To build all this, we use quadruples decribing segments of the list of
458 case bodies, containing the following fields:
459 1. an IdSet containing the environment variables free in the case bodies
460 2. a list of expressions of the form (Left|Right)* ((xs)*ts), to be put
461 into the case replacing the commands
462 3. a sum type that is the common type of these expressions, and also the
463 input type of the arrow
464 4. a CoreExpr for an arrow built by combining the translated command
468 dsCmd ids local_vars env_ids stack res_ty (HsCase exp (MatchGroup matches match_ty)) = do
469 core_exp <- dsLExpr exp
470 stack_ids <- mapM newSysLocalDs stack
472 -- Extract and desugar the leaf commands in the case, building tuple
473 -- expressions that will (after tagging) replace these leaves
476 leaves = concatMap leavesMatch matches
477 make_branch (leaf, bound_vars) = do
478 (core_leaf, fvs, leaf_ids) <-
479 dsfixCmd ids (local_vars `unionVarSet` bound_vars) stack res_ty leaf
480 return (fvs `minusVarSet` bound_vars,
481 [noLoc $ mkHsEnvStackExpr leaf_ids stack_ids],
482 envStackType leaf_ids stack,
485 branches <- mapM make_branch leaves
486 either_con <- dsLookupTyCon eitherTyConName
487 left_con <- dsLookupDataCon leftDataConName
488 right_con <- dsLookupDataCon rightDataConName
490 left_id = HsVar (dataConWrapId left_con)
491 right_id = HsVar (dataConWrapId right_con)
492 left_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ HsWrap (mkWpTyApps [ty1, ty2]) left_id ) e
493 right_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ HsWrap (mkWpTyApps [ty1, ty2]) right_id) e
495 -- Prefix each tuple with a distinct series of Left's and Right's,
496 -- in a balanced way, keeping track of the types.
498 merge_branches (fvs1, builds1, in_ty1, core_exp1)
499 (fvs2, builds2, in_ty2, core_exp2)
500 = (fvs1 `unionVarSet` fvs2,
501 map (left_expr in_ty1 in_ty2) builds1 ++
502 map (right_expr in_ty1 in_ty2) builds2,
503 mkTyConApp either_con [in_ty1, in_ty2],
504 do_choice ids in_ty1 in_ty2 res_ty core_exp1 core_exp2)
505 (fvs_alts, leaves', sum_ty, core_choices)
506 = foldb merge_branches branches
508 -- Replace the commands in the case with these tagged tuples,
509 -- yielding a HsExpr Id we can feed to dsExpr.
511 (_, matches') = mapAccumL (replaceLeavesMatch res_ty) leaves' matches
512 in_ty = envStackType env_ids stack
513 fvs_exp = exprFreeVars core_exp `intersectVarSet` local_vars
515 pat_ty = funArgTy match_ty
516 match_ty' = mkFunTy pat_ty sum_ty
517 -- Note that we replace the HsCase result type by sum_ty,
518 -- which is the type of matches'
520 core_body <- dsExpr (HsCase exp (MatchGroup matches' match_ty'))
521 core_matches <- matchEnvStack env_ids stack_ids core_body
522 return (do_map_arrow ids in_ty sum_ty res_ty core_matches core_choices,
523 fvs_exp `unionVarSet` fvs_alts)
525 -- A | ys |- c :: [ts] t
526 -- ----------------------------------
527 -- A | xs |- let binds in c :: [ts] t
529 -- ---> arr (\ ((xs)*ts) -> let binds in ((ys)*ts)) >>> c
531 dsCmd ids local_vars env_ids stack res_ty (HsLet binds body) = do
533 defined_vars = mkVarSet (map unLoc (collectLocalBinders binds))
534 local_vars' = local_vars `unionVarSet` defined_vars
536 (core_body, _free_vars, env_ids') <- dsfixCmd ids local_vars' stack res_ty body
537 stack_ids <- mapM newSysLocalDs stack
538 -- build a new environment, plus the stack, using the let bindings
539 core_binds <- dsLocalBinds binds (buildEnvStack env_ids' stack_ids)
540 -- match the old environment and stack against the input
541 core_map <- matchEnvStack env_ids stack_ids core_binds
542 return (do_map_arrow ids
543 (envStackType env_ids stack)
544 (envStackType env_ids' stack)
548 exprFreeVars core_binds `intersectVarSet` local_vars)
550 dsCmd ids local_vars env_ids [] res_ty (HsDo _ctxt stmts body _)
551 = dsCmdDo ids local_vars env_ids res_ty stmts body
553 -- A |- e :: forall e. a1 (e*ts1) t1 -> ... an (e*tsn) tn -> a (e*ts) t
554 -- A | xs |- ci :: [tsi] ti
555 -- -----------------------------------
556 -- A | xs |- (|e c1 ... cn|) :: [ts] t ---> e [t_xs] c1 ... cn
558 dsCmd _ids local_vars env_ids _stack _res_ty (HsArrForm op _ args) = do
559 let env_ty = mkBigCoreVarTupTy env_ids
560 core_op <- dsLExpr op
561 (core_args, fv_sets) <- mapAndUnzipM (dsTrimCmdArg local_vars env_ids) args
562 return (mkApps (App core_op (Type env_ty)) core_args,
563 unionVarSets fv_sets)
566 dsCmd ids local_vars env_ids stack res_ty (HsTick ix vars expr) = do
567 (expr1,id_set) <- dsLCmd ids local_vars env_ids stack res_ty expr
568 expr2 <- mkTickBox ix vars expr1
569 return (expr2,id_set)
571 dsCmd _ _ _ _ _ c = pprPanic "dsCmd" (ppr c)
573 -- A | ys |- c :: [ts] t (ys <= xs)
574 -- ---------------------
575 -- A | xs |- c :: [ts] t ---> arr_ts (\ (xs) -> (ys)) >>> c
578 :: IdSet -- set of local vars available to this command
579 -> [Id] -- list of vars in the input to this command
580 -> LHsCmdTop Id -- command argument to desugar
581 -> DsM (CoreExpr, -- desugared expression
582 IdSet) -- set of local vars that occur free
583 dsTrimCmdArg local_vars env_ids (L _ (HsCmdTop cmd stack cmd_ty ids)) = do
584 meth_ids <- mkCmdEnv ids
585 (core_cmd, free_vars, env_ids') <- dsfixCmd meth_ids local_vars stack cmd_ty cmd
586 stack_ids <- mapM newSysLocalDs stack
587 trim_code <- matchEnvStack env_ids stack_ids (buildEnvStack env_ids' stack_ids)
589 in_ty = envStackType env_ids stack
590 in_ty' = envStackType env_ids' stack
591 arg_code = if env_ids' == env_ids then core_cmd else
592 do_map_arrow meth_ids in_ty in_ty' cmd_ty trim_code core_cmd
593 return (bindCmdEnv meth_ids arg_code, free_vars)
595 -- Given A | xs |- c :: [ts] t, builds c with xs fed back.
596 -- Typically needs to be prefixed with arr (\p -> ((xs)*ts))
599 :: DsCmdEnv -- arrow combinators
600 -> IdSet -- set of local vars available to this command
601 -> [Type] -- type of the stack
602 -> Type -- return type of the command
603 -> LHsCmd Id -- command to desugar
604 -> DsM (CoreExpr, -- desugared expression
605 IdSet, -- set of local vars that occur free
606 [Id]) -- set as a list, fed back
607 dsfixCmd ids local_vars stack cmd_ty cmd
608 = fixDs (\ ~(_,_,env_ids') -> do
609 (core_cmd, free_vars) <- dsLCmd ids local_vars env_ids' stack cmd_ty cmd
610 return (core_cmd, free_vars, varSetElems free_vars))
614 Translation of command judgements of the form
616 A | xs |- do { ss } :: [] t
620 dsCmdDo :: DsCmdEnv -- arrow combinators
621 -> IdSet -- set of local vars available to this statement
622 -> [Id] -- list of vars in the input to this statement
623 -- This is typically fed back,
624 -- so don't pull on it too early
625 -> Type -- return type of the statement
626 -> [LStmt Id] -- statements to desugar
627 -> LHsExpr Id -- body
628 -> DsM (CoreExpr, -- desugared expression
629 IdSet) -- set of local vars that occur free
631 -- A | xs |- c :: [] t
632 -- --------------------------
633 -- A | xs |- do { c } :: [] t
635 dsCmdDo ids local_vars env_ids res_ty [] body
636 = dsLCmd ids local_vars env_ids [] res_ty body
638 dsCmdDo ids local_vars env_ids res_ty (stmt:stmts) body = do
640 bound_vars = mkVarSet (map unLoc (collectLStmtBinders stmt))
641 local_vars' = local_vars `unionVarSet` bound_vars
642 (core_stmts, _, env_ids') <- fixDs (\ ~(_,_,env_ids') -> do
643 (core_stmts, fv_stmts) <- dsCmdDo ids local_vars' env_ids' res_ty stmts body
644 return (core_stmts, fv_stmts, varSetElems fv_stmts))
645 (core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids env_ids' stmt
646 return (do_compose ids
647 (mkBigCoreVarTupTy env_ids)
648 (mkBigCoreVarTupTy env_ids')
655 A statement maps one local environment to another, and is represented
656 as an arrow from one tuple type to another. A statement sequence is
657 translated to a composition of such arrows.
659 dsCmdLStmt :: DsCmdEnv -> IdSet -> [Id] -> [Id] -> LStmt Id
660 -> DsM (CoreExpr, IdSet)
661 dsCmdLStmt ids local_vars env_ids out_ids cmd
662 = dsCmdStmt ids local_vars env_ids out_ids (unLoc cmd)
665 :: DsCmdEnv -- arrow combinators
666 -> IdSet -- set of local vars available to this statement
667 -> [Id] -- list of vars in the input to this statement
668 -- This is typically fed back,
669 -- so don't pull on it too early
670 -> [Id] -- list of vars in the output of this statement
671 -> Stmt Id -- statement to desugar
672 -> DsM (CoreExpr, -- desugared expression
673 IdSet) -- set of local vars that occur free
675 -- A | xs1 |- c :: [] t
676 -- A | xs' |- do { ss } :: [] t'
677 -- ------------------------------
678 -- A | xs |- do { c; ss } :: [] t'
680 -- ---> arr (\ (xs) -> ((xs1),(xs'))) >>> first c >>>
683 dsCmdStmt ids local_vars env_ids out_ids (ExprStmt cmd _ c_ty) = do
684 (core_cmd, fv_cmd, env_ids1) <- dsfixCmd ids local_vars [] c_ty cmd
685 core_mux <- matchEnvStack env_ids []
686 (mkCorePairExpr (mkBigCoreVarTup env_ids1) (mkBigCoreVarTup out_ids))
688 in_ty = mkBigCoreVarTupTy env_ids
689 in_ty1 = mkBigCoreVarTupTy env_ids1
690 out_ty = mkBigCoreVarTupTy out_ids
691 before_c_ty = mkCorePairTy in_ty1 out_ty
692 after_c_ty = mkCorePairTy c_ty out_ty
693 snd_fn <- mkSndExpr c_ty out_ty
694 return (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
695 do_compose ids before_c_ty after_c_ty out_ty
696 (do_first ids in_ty1 c_ty out_ty core_cmd) $
697 do_arr ids after_c_ty out_ty snd_fn,
698 extendVarSetList fv_cmd out_ids)
701 -- A | xs1 |- c :: [] t
702 -- A | xs' |- do { ss } :: [] t' xs2 = xs' - defs(p)
703 -- -----------------------------------
704 -- A | xs |- do { p <- c; ss } :: [] t'
706 -- ---> arr (\ (xs) -> ((xs1),(xs2))) >>> first c >>>
707 -- arr (\ (p, (xs2)) -> (xs')) >>> ss
709 -- It would be simpler and more consistent to do this using second,
710 -- but that's likely to be defined in terms of first.
712 dsCmdStmt ids local_vars env_ids out_ids (BindStmt pat cmd _ _) = do
713 (core_cmd, fv_cmd, env_ids1) <- dsfixCmd ids local_vars [] (hsLPatType pat) cmd
715 pat_ty = hsLPatType pat
716 pat_vars = mkVarSet (collectPatBinders pat)
717 env_ids2 = varSetElems (mkVarSet out_ids `minusVarSet` pat_vars)
718 env_ty2 = mkBigCoreVarTupTy env_ids2
720 -- multiplexing function
721 -- \ (xs) -> ((xs1),(xs2))
723 core_mux <- matchEnvStack env_ids []
724 (mkCorePairExpr (mkBigCoreVarTup env_ids1) (mkBigCoreVarTup env_ids2))
726 -- projection function
727 -- \ (p, (xs2)) -> (zs)
729 env_id <- newSysLocalDs env_ty2
730 uniqs <- newUniqueSupply
732 after_c_ty = mkCorePairTy pat_ty env_ty2
733 out_ty = mkBigCoreVarTupTy out_ids
734 body_expr = coreCaseTuple uniqs env_id env_ids2 (mkBigCoreVarTup out_ids)
736 fail_expr <- mkFailExpr (StmtCtxt DoExpr) out_ty
737 pat_id <- selectSimpleMatchVarL pat
738 match_code <- matchSimply (Var pat_id) (StmtCtxt DoExpr) pat body_expr fail_expr
739 pair_id <- newSysLocalDs after_c_ty
741 proj_expr = Lam pair_id (coreCasePair pair_id pat_id env_id match_code)
743 -- put it all together
745 in_ty = mkBigCoreVarTupTy env_ids
746 in_ty1 = mkBigCoreVarTupTy env_ids1
747 in_ty2 = mkBigCoreVarTupTy env_ids2
748 before_c_ty = mkCorePairTy in_ty1 in_ty2
749 return (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
750 do_compose ids before_c_ty after_c_ty out_ty
751 (do_first ids in_ty1 pat_ty in_ty2 core_cmd) $
752 do_arr ids after_c_ty out_ty proj_expr,
753 fv_cmd `unionVarSet` (mkVarSet out_ids `minusVarSet` pat_vars))
755 -- A | xs' |- do { ss } :: [] t
756 -- --------------------------------------
757 -- A | xs |- do { let binds; ss } :: [] t
759 -- ---> arr (\ (xs) -> let binds in (xs')) >>> ss
761 dsCmdStmt ids local_vars env_ids out_ids (LetStmt binds) = do
762 -- build a new environment using the let bindings
763 core_binds <- dsLocalBinds binds (mkBigCoreVarTup out_ids)
764 -- match the old environment against the input
765 core_map <- matchEnvStack env_ids [] core_binds
767 (mkBigCoreVarTupTy env_ids)
768 (mkBigCoreVarTupTy out_ids)
770 exprFreeVars core_binds `intersectVarSet` local_vars)
772 -- A | ys |- do { ss; returnA -< ((xs1), (ys2)) } :: [] ...
773 -- A | xs' |- do { ss' } :: [] t
774 -- ------------------------------------
775 -- A | xs |- do { rec ss; ss' } :: [] t
777 -- xs1 = xs' /\ defs(ss)
778 -- xs2 = xs' - defs(ss)
779 -- ys1 = ys - defs(ss)
780 -- ys2 = ys /\ defs(ss)
782 -- ---> arr (\(xs) -> ((ys1),(xs2))) >>>
783 -- first (loop (arr (\((ys1),~(ys2)) -> (ys)) >>> ss)) >>>
784 -- arr (\((xs1),(xs2)) -> (xs')) >>> ss'
786 dsCmdStmt ids local_vars env_ids out_ids (RecStmt stmts later_ids rec_ids rhss _binds) = do
787 let -- ToDo: ****** binds not desugared; ROSS PLEASE FIX ********
788 env2_id_set = mkVarSet out_ids `minusVarSet` mkVarSet later_ids
789 env2_ids = varSetElems env2_id_set
790 env2_ty = mkBigCoreVarTupTy env2_ids
792 -- post_loop_fn = \((later_ids),(env2_ids)) -> (out_ids)
794 uniqs <- newUniqueSupply
795 env2_id <- newSysLocalDs env2_ty
797 later_ty = mkBigCoreVarTupTy later_ids
798 post_pair_ty = mkCorePairTy later_ty env2_ty
799 post_loop_body = coreCaseTuple uniqs env2_id env2_ids (mkBigCoreVarTup out_ids)
801 post_loop_fn <- matchEnvStack later_ids [env2_id] post_loop_body
805 (core_loop, env1_id_set, env1_ids)
806 <- dsRecCmd ids local_vars stmts later_ids rec_ids rhss
808 -- pre_loop_fn = \(env_ids) -> ((env1_ids),(env2_ids))
811 env1_ty = mkBigCoreVarTupTy env1_ids
812 pre_pair_ty = mkCorePairTy env1_ty env2_ty
813 pre_loop_body = mkCorePairExpr (mkBigCoreVarTup env1_ids)
814 (mkBigCoreVarTup env2_ids)
816 pre_loop_fn <- matchEnvStack env_ids [] pre_loop_body
818 -- arr pre_loop_fn >>> first (loop (...)) >>> arr post_loop_fn
821 env_ty = mkBigCoreVarTupTy env_ids
822 out_ty = mkBigCoreVarTupTy out_ids
823 core_body = do_map_arrow ids env_ty pre_pair_ty out_ty
825 (do_compose ids pre_pair_ty post_pair_ty out_ty
826 (do_first ids env1_ty later_ty env2_ty
828 (do_arr ids post_pair_ty out_ty
831 return (core_body, env1_id_set `unionVarSet` env2_id_set)
833 dsCmdStmt _ _ _ _ s = pprPanic "dsCmdStmt" (ppr s)
835 -- loop (arr (\ ((env1_ids), ~(rec_ids)) -> (env_ids)) >>>
837 -- arr (\ (out_ids) -> ((later_ids),(rhss))) >>>
839 dsRecCmd :: DsCmdEnv -> VarSet -> [LStmt Id] -> [Var] -> [Var] -> [HsExpr Id]
840 -> DsM (CoreExpr, VarSet, [Var])
841 dsRecCmd ids local_vars stmts later_ids rec_ids rhss = do
843 rec_id_set = mkVarSet rec_ids
844 out_ids = varSetElems (mkVarSet later_ids `unionVarSet` rec_id_set)
845 out_ty = mkBigCoreVarTupTy out_ids
846 local_vars' = local_vars `unionVarSet` rec_id_set
848 -- mk_pair_fn = \ (out_ids) -> ((later_ids),(rhss))
850 core_rhss <- mapM dsExpr rhss
852 later_tuple = mkBigCoreVarTup later_ids
853 later_ty = mkBigCoreVarTupTy later_ids
854 rec_tuple = mkBigCoreTup core_rhss
855 rec_ty = mkBigCoreVarTupTy rec_ids
856 out_pair = mkCorePairExpr later_tuple rec_tuple
857 out_pair_ty = mkCorePairTy later_ty rec_ty
859 mk_pair_fn <- matchEnvStack out_ids [] out_pair
863 (core_stmts, fv_stmts, env_ids) <- dsfixCmdStmts ids local_vars' out_ids stmts
865 -- squash_pair_fn = \ ((env1_ids), ~(rec_ids)) -> (env_ids)
867 rec_id <- newSysLocalDs rec_ty
869 env1_id_set = fv_stmts `minusVarSet` rec_id_set
870 env1_ids = varSetElems env1_id_set
871 env1_ty = mkBigCoreVarTupTy env1_ids
872 in_pair_ty = mkCorePairTy env1_ty rec_ty
873 core_body = mkBigCoreTup (map selectVar env_ids)
876 | v `elemVarSet` rec_id_set
877 = mkTupleSelector rec_ids v rec_id (Var rec_id)
880 squash_pair_fn <- matchEnvStack env1_ids [rec_id] core_body
882 -- loop (arr squash_pair_fn >>> ss >>> arr mk_pair_fn)
885 env_ty = mkBigCoreVarTupTy env_ids
886 core_loop = do_loop ids env1_ty later_ty rec_ty
887 (do_map_arrow ids in_pair_ty env_ty out_pair_ty
889 (do_compose ids env_ty out_ty out_pair_ty
891 (do_arr ids out_ty out_pair_ty mk_pair_fn)))
893 return (core_loop, env1_id_set, env1_ids)
896 A sequence of statements (as in a rec) is desugared to an arrow between
901 :: DsCmdEnv -- arrow combinators
902 -> IdSet -- set of local vars available to this statement
903 -> [Id] -- output vars of these statements
904 -> [LStmt Id] -- statements to desugar
905 -> DsM (CoreExpr, -- desugared expression
906 IdSet, -- set of local vars that occur free
909 dsfixCmdStmts ids local_vars out_ids stmts
910 = fixDs (\ ~(_,_,env_ids) -> do
911 (core_stmts, fv_stmts) <- dsCmdStmts ids local_vars env_ids out_ids stmts
912 return (core_stmts, fv_stmts, varSetElems fv_stmts))
915 :: DsCmdEnv -- arrow combinators
916 -> IdSet -- set of local vars available to this statement
917 -> [Id] -- list of vars in the input to these statements
918 -> [Id] -- output vars of these statements
919 -> [LStmt Id] -- statements to desugar
920 -> DsM (CoreExpr, -- desugared expression
921 IdSet) -- set of local vars that occur free
923 dsCmdStmts ids local_vars env_ids out_ids [stmt]
924 = dsCmdLStmt ids local_vars env_ids out_ids stmt
926 dsCmdStmts ids local_vars env_ids out_ids (stmt:stmts) = do
928 bound_vars = mkVarSet (map unLoc (collectLStmtBinders stmt))
929 local_vars' = local_vars `unionVarSet` bound_vars
930 (core_stmts, _fv_stmts, env_ids') <- dsfixCmdStmts ids local_vars' out_ids stmts
931 (core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids env_ids' stmt
932 return (do_compose ids
933 (mkBigCoreVarTupTy env_ids)
934 (mkBigCoreVarTupTy env_ids')
935 (mkBigCoreVarTupTy out_ids)
940 dsCmdStmts _ _ _ _ [] = panic "dsCmdStmts []"
944 Match a list of expressions against a list of patterns, left-to-right.
947 matchSimplys :: [CoreExpr] -- Scrutinees
948 -> HsMatchContext Name -- Match kind
949 -> [LPat Id] -- Patterns they should match
950 -> CoreExpr -- Return this if they all match
951 -> CoreExpr -- Return this if they don't
953 matchSimplys [] _ctxt [] result_expr _fail_expr = return result_expr
954 matchSimplys (exp:exps) ctxt (pat:pats) result_expr fail_expr = do
955 match_code <- matchSimplys exps ctxt pats result_expr fail_expr
956 matchSimply exp ctxt pat match_code fail_expr
957 matchSimplys _ _ _ _ _ = panic "matchSimplys"
960 List of leaf expressions, with set of variables bound in each
963 leavesMatch :: LMatch Id -> [(LHsExpr Id, IdSet)]
964 leavesMatch (L _ (Match pats _ (GRHSs grhss binds)))
966 defined_vars = mkVarSet (collectPatsBinders pats)
968 mkVarSet (map unLoc (collectLocalBinders binds))
971 mkVarSet (map unLoc (collectLStmtsBinders stmts))
972 `unionVarSet` defined_vars)
973 | L _ (GRHS stmts expr) <- grhss]
976 Replace the leaf commands in a match
980 :: Type -- new result type
981 -> [LHsExpr Id] -- replacement leaf expressions of that type
982 -> LMatch Id -- the matches of a case command
983 -> ([LHsExpr Id],-- remaining leaf expressions
984 LMatch Id) -- updated match
985 replaceLeavesMatch _res_ty leaves (L loc (Match pat mt (GRHSs grhss binds)))
987 (leaves', grhss') = mapAccumL replaceLeavesGRHS leaves grhss
989 (leaves', L loc (Match pat mt (GRHSs grhss' binds)))
992 :: [LHsExpr Id] -- replacement leaf expressions of that type
993 -> LGRHS Id -- rhss of a case command
994 -> ([LHsExpr Id],-- remaining leaf expressions
995 LGRHS Id) -- updated GRHS
996 replaceLeavesGRHS (leaf:leaves) (L loc (GRHS stmts _))
997 = (leaves, L loc (GRHS stmts leaf))
998 replaceLeavesGRHS [] _ = panic "replaceLeavesGRHS []"
1001 Balanced fold of a non-empty list.
1004 foldb :: (a -> a -> a) -> [a] -> a
1005 foldb _ [] = error "foldb of empty list"
1007 foldb f xs = foldb f (fold_pairs xs)
1010 fold_pairs [x] = [x]
1011 fold_pairs (x1:x2:xs) = f x1 x2:fold_pairs xs
1014 The following functions to collect value variables from patterns are
1015 copied from HsUtils, with one change: we also collect the dictionary
1016 bindings (pat_binds) from ConPatOut. We need them for cases like
1018 h :: Arrow a => Int -> a (Int,Int) Int
1019 h x = proc (y,z) -> case compare x y of
1020 GT -> returnA -< z+x
1022 The type checker turns the case into
1025 GT { p77 = plusInt } -> returnA -< p77 z x
1027 Here p77 is a local binding for the (+) operation.
1029 See comments in HsUtils for why the other version does not include
1033 collectPatBinders :: OutputableBndr a => LPat a -> [a]
1034 collectPatBinders pat = map unLoc (collectLocatedPatBinders pat)
1036 collectLocatedPatBinders :: OutputableBndr a => LPat a -> [Located a]
1037 collectLocatedPatBinders pat = collectl pat []
1039 collectPatsBinders :: OutputableBndr a => [LPat a] -> [a]
1040 collectPatsBinders pats = map unLoc (collectLocatedPatsBinders pats)
1042 collectLocatedPatsBinders :: OutputableBndr a => [LPat a] -> [Located a]
1043 collectLocatedPatsBinders pats = foldr collectl [] pats
1045 ---------------------
1046 collectl :: OutputableBndr a => LPat a -> [Located a] -> [Located a]
1047 collectl (L l pat) bndrs
1050 go (VarPat var) = L l var : bndrs
1051 go (VarPatOut var bs) = L l var : collectHsBindLocatedBinders bs
1053 go (WildPat _) = bndrs
1054 go (LazyPat pat) = collectl pat bndrs
1055 go (BangPat pat) = collectl pat bndrs
1056 go (AsPat a pat) = a : collectl pat bndrs
1057 go (ParPat pat) = collectl pat bndrs
1059 go (ListPat pats _) = foldr collectl bndrs pats
1060 go (PArrPat pats _) = foldr collectl bndrs pats
1061 go (TuplePat pats _ _) = foldr collectl bndrs pats
1063 go (ConPatIn _ ps) = foldr collectl bndrs (hsConPatArgs ps)
1064 go (ConPatOut {pat_args=ps, pat_binds=ds}) =
1065 collectHsBindLocatedBinders ds
1066 ++ foldr collectl bndrs (hsConPatArgs ps)
1067 go (LitPat _) = bndrs
1068 go (NPat _ _ _) = bndrs
1069 go (NPlusKPat n _ _ _) = n : bndrs
1071 go (SigPatIn pat _) = collectl pat bndrs
1072 go (SigPatOut pat _) = collectl pat bndrs
1073 go (TypePat _) = bndrs
1074 go (CoPat _ pat _) = collectl (noLoc pat) bndrs
1075 go p = pprPanic "collectl/go" (ppr p)