2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[DsArrows]{Desugaring arrow commands}
7 module DsArrows ( dsProcExpr ) where
9 #include "HsVersions.h"
11 import Match ( matchSimply )
12 import DsUtils ( mkErrorAppDs,
13 mkCoreTupTy, mkCoreTup, selectMatchVarL,
14 mkTupleCase, mkBigCoreTup, mkTupleType,
15 mkTupleExpr, mkTupleSelector,
16 dsReboundNames, lookupReboundName )
20 import TcHsSyn ( hsPatType )
22 -- NB: The desugarer, which straddles the source and Core worlds, sometimes
23 -- needs to see source types (newtypes etc), and sometimes not
24 -- So WATCH OUT; check each use of split*Ty functions.
25 -- Sigh. This is a pain.
27 import {-# SOURCE #-} DsExpr ( dsExpr, dsLExpr, dsLet )
29 import TcType ( Type, tcSplitAppTy )
30 import Type ( mkTyConApp )
32 import CoreFVs ( exprFreeVars )
33 import CoreUtils ( mkIfThenElse, bindNonRec, exprType )
35 import Id ( Id, idType )
37 import PrelInfo ( pAT_ERROR_ID )
38 import DataCon ( dataConWrapId )
39 import TysWiredIn ( tupleCon )
40 import BasicTypes ( Boxity(..) )
41 import PrelNames ( eitherTyConName, leftDataConName, rightDataConName,
42 arrAName, composeAName, firstAName,
43 appAName, choiceAName, loopAName )
44 import Util ( mapAccumL )
47 import HsPat ( collectPatBinders, collectPatsBinders )
48 import VarSet ( IdSet, mkVarSet, varSetElems,
49 intersectVarSet, minusVarSet, extendVarSetList,
50 unionVarSet, unionVarSets, elemVarSet )
51 import SrcLoc ( Located(..), unLoc, noLoc, getLoc )
55 data DsCmdEnv = DsCmdEnv {
56 meth_binds :: [CoreBind],
57 arr_id, compose_id, first_id, app_id, choice_id, loop_id :: CoreExpr
60 mkCmdEnv :: ReboundNames Id -> DsM DsCmdEnv
62 = dsReboundNames ids `thenDs` \ (meth_binds, ds_meths) ->
64 meth_binds = meth_binds,
65 arr_id = lookupReboundName ds_meths arrAName,
66 compose_id = lookupReboundName ds_meths composeAName,
67 first_id = lookupReboundName ds_meths firstAName,
68 app_id = lookupReboundName ds_meths appAName,
69 choice_id = lookupReboundName ds_meths choiceAName,
70 loop_id = lookupReboundName ds_meths loopAName
73 bindCmdEnv :: DsCmdEnv -> CoreExpr -> CoreExpr
74 bindCmdEnv ids body = foldr Let body (meth_binds ids)
76 -- arr :: forall b c. (b -> c) -> a b c
77 do_arr :: DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
78 do_arr ids b_ty c_ty f = mkApps (arr_id ids) [Type b_ty, Type c_ty, f]
80 -- (>>>) :: forall b c d. a b c -> a c d -> a b d
81 do_compose :: DsCmdEnv -> Type -> Type -> Type ->
82 CoreExpr -> CoreExpr -> CoreExpr
83 do_compose ids b_ty c_ty d_ty f g
84 = mkApps (compose_id ids) [Type b_ty, Type c_ty, Type d_ty, f, g]
86 -- first :: forall b c d. a b c -> a (b,d) (c,d)
87 do_first :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
88 do_first ids b_ty c_ty d_ty f
89 = mkApps (first_id ids) [Type b_ty, Type c_ty, Type d_ty, f]
91 -- app :: forall b c. a (a b c, b) c
92 do_app :: DsCmdEnv -> Type -> Type -> CoreExpr
93 do_app ids b_ty c_ty = mkApps (app_id ids) [Type b_ty, Type c_ty]
95 -- (|||) :: forall b d c. a b d -> a c d -> a (Either b c) d
96 -- note the swapping of d and c
97 do_choice :: DsCmdEnv -> Type -> Type -> Type ->
98 CoreExpr -> CoreExpr -> CoreExpr
99 do_choice ids b_ty c_ty d_ty f g
100 = mkApps (choice_id ids) [Type b_ty, Type d_ty, Type c_ty, f, g]
102 -- loop :: forall b d c. a (b,d) (c,d) -> a b c
103 -- note the swapping of d and c
104 do_loop :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
105 do_loop ids b_ty c_ty d_ty f
106 = mkApps (loop_id ids) [Type b_ty, Type d_ty, Type c_ty, f]
108 -- map_arrow (f :: b -> c) (g :: a c d) = arr f >>> g :: a b d
109 do_map_arrow :: DsCmdEnv -> Type -> Type -> Type ->
110 CoreExpr -> CoreExpr -> CoreExpr
111 do_map_arrow ids b_ty c_ty d_ty f c
112 = do_compose ids b_ty c_ty d_ty (do_arr ids b_ty c_ty f) c
114 mkFailExpr :: HsMatchContext Id -> Type -> DsM CoreExpr
116 = mkErrorAppDs pAT_ERROR_ID ty (matchContextErrString ctxt)
118 -- construct CoreExpr for \ (a :: a_ty, b :: b_ty) -> b
119 mkSndExpr :: Type -> Type -> DsM CoreExpr
121 = newSysLocalDs a_ty `thenDs` \ a_var ->
122 newSysLocalDs b_ty `thenDs` \ b_var ->
123 newSysLocalDs (mkCorePairTy a_ty b_ty) `thenDs` \ pair_var ->
124 returnDs (Lam pair_var
125 (coreCasePair pair_var a_var b_var (Var b_var)))
128 Build case analysis of a tuple. This cannot be done in the DsM monad,
129 because the list of variables is typically not yet defined.
132 -- coreCaseTuple [u1..] v [x1..xn] body
133 -- = case v of v { (x1, .., xn) -> body }
134 -- But the matching may be nested if the tuple is very big
136 coreCaseTuple :: UniqSupply -> Id -> [Id] -> CoreExpr -> CoreExpr
137 coreCaseTuple uniqs scrut_var vars body
138 = mkTupleCase uniqs vars body scrut_var (Var scrut_var)
140 coreCasePair :: Id -> Id -> Id -> CoreExpr -> CoreExpr
141 coreCasePair scrut_var var1 var2 body
142 = Case (Var scrut_var) scrut_var
143 [(DataAlt (tupleCon Boxed 2), [var1, var2], body)]
147 mkCorePairTy :: Type -> Type -> Type
148 mkCorePairTy t1 t2 = mkCoreTupTy [t1, t2]
150 mkCorePairExpr :: CoreExpr -> CoreExpr -> CoreExpr
151 mkCorePairExpr e1 e2 = mkCoreTup [e1, e2]
154 The input is divided into a local environment, which is a flat tuple
155 (unless it's too big), and a stack, each element of which is paired
156 with the stack in turn. In general, the input has the form
158 (...((x1,...,xn),s1),...sk)
160 where xi are the environment values, and si the ones on the stack,
161 with s1 being the "top", the first one to be matched with a lambda.
164 envStackType :: [Id] -> [Type] -> Type
165 envStackType ids stack_tys = foldl mkCorePairTy (mkTupleType ids) stack_tys
167 ----------------------------------------------
170 -- (...((x1,...,xn),s1),...sk)
172 buildEnvStack :: [Id] -> [Id] -> CoreExpr
173 buildEnvStack env_ids stack_ids
174 = foldl mkCorePairExpr (mkTupleExpr env_ids) (map Var stack_ids)
176 ----------------------------------------------
179 -- \ (...((x1,...,xn),s1),...sk) -> e
182 -- case zk of (zk-1,sk) ->
184 -- case z1 of (z0,s1) ->
185 -- case z0 of (x1,...,xn) ->
188 matchEnvStack :: [Id] -- x1..xn
192 matchEnvStack env_ids stack_ids body
193 = newUniqueSupply `thenDs` \ uniqs ->
194 newSysLocalDs (mkTupleType env_ids) `thenDs` \ tup_var ->
195 matchVarStack tup_var stack_ids
196 (coreCaseTuple uniqs tup_var env_ids body)
199 ----------------------------------------------
202 -- \ (...(z0,s1),...sk) -> e
205 -- case zk of (zk-1,sk) ->
207 -- case z1 of (z0,s1) ->
210 matchVarStack :: Id -- z0
214 matchVarStack env_id [] body
215 = returnDs (Lam env_id body)
216 matchVarStack env_id (stack_id:stack_ids) body
217 = newSysLocalDs (mkCorePairTy (idType env_id) (idType stack_id))
218 `thenDs` \ pair_id ->
219 matchVarStack pair_id stack_ids
220 (coreCasePair pair_id env_id stack_id body)
224 mkHsTupleExpr :: [HsExpr Id] -> HsExpr Id
225 mkHsTupleExpr [e] = e
226 mkHsTupleExpr es = ExplicitTuple (map noLoc es) Boxed
228 mkHsPairExpr :: HsExpr Id -> HsExpr Id -> HsExpr Id
229 mkHsPairExpr e1 e2 = mkHsTupleExpr [e1, e2]
231 mkHsEnvStackExpr :: [Id] -> [Id] -> HsExpr Id
232 mkHsEnvStackExpr env_ids stack_ids
233 = foldl mkHsPairExpr (mkHsTupleExpr (map HsVar env_ids)) (map HsVar stack_ids)
236 Translation of arrow abstraction
240 -- A | xs |- c :: [] t' ---> c'
241 -- --------------------------
242 -- A |- proc p -> c :: a t t' ---> arr (\ p -> (xs)) >>> c'
244 -- where (xs) is the tuple of variables bound by p
250 dsProcExpr pat (L _ (HsCmdTop cmd [] cmd_ty ids))
251 = mkCmdEnv ids `thenDs` \ meth_ids ->
253 locals = mkVarSet (collectPatBinders pat)
255 dsfixCmd meth_ids locals [] cmd_ty cmd
256 `thenDs` \ (core_cmd, free_vars, env_ids) ->
258 env_ty = mkTupleType env_ids
260 mkFailExpr ProcExpr env_ty `thenDs` \ fail_expr ->
261 selectMatchVarL pat `thenDs` \ var ->
262 matchSimply (Var var) ProcExpr pat (mkTupleExpr env_ids) fail_expr
263 `thenDs` \ match_code ->
265 pat_ty = hsPatType pat
266 proc_code = do_map_arrow meth_ids pat_ty env_ty cmd_ty
270 returnDs (bindCmdEnv meth_ids proc_code)
273 Translation of command judgements of the form
275 A | xs |- c :: [ts] t
278 dsLCmd ids local_vars env_ids stack res_ty cmd
279 = dsCmd ids local_vars env_ids stack res_ty (unLoc cmd)
281 dsCmd :: DsCmdEnv -- arrow combinators
282 -> IdSet -- set of local vars available to this command
283 -> [Id] -- list of vars in the input to this command
284 -- This is typically fed back,
285 -- so don't pull on it too early
286 -> [Type] -- type of the stack
287 -> Type -- return type of the command
288 -> HsCmd Id -- command to desugar
289 -> DsM (CoreExpr, -- desugared expression
290 IdSet) -- set of local vars that occur free
292 -- A |- f :: a (t*ts) t'
294 -- -----------------------------
295 -- A | xs |- f -< arg :: [ts] t'
297 -- ---> arr (\ ((xs)*ts) -> (arg*ts)) >>> f
299 dsCmd ids local_vars env_ids stack res_ty
300 (HsArrApp arrow arg arrow_ty HsFirstOrderApp _)
302 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
303 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
304 env_ty = mkTupleType env_ids
306 dsLExpr arrow `thenDs` \ core_arrow ->
307 dsLExpr arg `thenDs` \ core_arg ->
308 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
309 matchEnvStack env_ids stack_ids
310 (foldl mkCorePairExpr core_arg (map Var stack_ids))
311 `thenDs` \ core_make_arg ->
312 returnDs (do_map_arrow ids
313 (envStackType env_ids stack)
318 exprFreeVars core_arg `intersectVarSet` local_vars)
320 -- A, xs |- f :: a (t*ts) t'
322 -- ------------------------------
323 -- A | xs |- f -<< arg :: [ts] t'
325 -- ---> arr (\ ((xs)*ts) -> (f,(arg*ts))) >>> app
327 dsCmd ids local_vars env_ids stack res_ty
328 (HsArrApp arrow arg arrow_ty HsHigherOrderApp _)
330 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
331 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
332 env_ty = mkTupleType env_ids
334 dsLExpr arrow `thenDs` \ core_arrow ->
335 dsLExpr arg `thenDs` \ core_arg ->
336 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
337 matchEnvStack env_ids stack_ids
338 (mkCorePairExpr core_arrow
339 (foldl mkCorePairExpr core_arg (map Var stack_ids)))
340 `thenDs` \ core_make_pair ->
341 returnDs (do_map_arrow ids
342 (envStackType env_ids stack)
343 (mkCorePairTy arrow_ty arg_ty)
346 (do_app ids arg_ty res_ty),
347 (exprFreeVars core_arrow `unionVarSet` exprFreeVars core_arg)
348 `intersectVarSet` local_vars)
350 -- A | ys |- c :: [t:ts] t'
352 -- ------------------------
353 -- A | xs |- c e :: [ts] t'
355 -- ---> arr (\ ((xs)*ts) -> let z = e in (((ys),z)*ts)) >>> c
357 dsCmd ids local_vars env_ids stack res_ty (HsApp cmd arg)
358 = dsLExpr arg `thenDs` \ core_arg ->
360 arg_ty = exprType core_arg
361 stack' = arg_ty:stack
363 dsfixCmd ids local_vars stack' res_ty cmd
364 `thenDs` \ (core_cmd, free_vars, env_ids') ->
365 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
366 newSysLocalDs arg_ty `thenDs` \ arg_id ->
367 -- push the argument expression onto the stack
369 core_body = bindNonRec arg_id core_arg
370 (buildEnvStack env_ids' (arg_id:stack_ids))
372 -- match the environment and stack against the input
373 matchEnvStack env_ids stack_ids core_body
374 `thenDs` \ core_map ->
375 returnDs (do_map_arrow ids
376 (envStackType env_ids stack)
377 (envStackType env_ids' stack')
381 (exprFreeVars core_arg `intersectVarSet` local_vars)
382 `unionVarSet` free_vars)
384 -- A | ys |- c :: [ts] t'
385 -- -----------------------------------------------
386 -- A | xs |- \ p1 ... pk -> c :: [t1:...:tk:ts] t'
388 -- ---> arr (\ ((((xs), p1), ... pk)*ts) -> ((ys)*ts)) >>> c
390 dsCmd ids local_vars env_ids stack res_ty
391 (HsLam (L _ (Match pats _ (GRHSs [L _ (GRHS [L _ (ResultStmt body)])] _ _cmd_ty))))
393 pat_vars = mkVarSet (collectPatsBinders pats)
394 local_vars' = local_vars `unionVarSet` pat_vars
395 stack' = drop (length pats) stack
397 dsfixCmd ids local_vars' stack' res_ty body
398 `thenDs` \ (core_body, free_vars, env_ids') ->
399 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
401 -- the expression is built from the inside out, so the actions
402 -- are presented in reverse order
405 (actual_ids, stack_ids') = splitAt (length pats) stack_ids
406 -- build a new environment, plus what's left of the stack
407 core_expr = buildEnvStack env_ids' stack_ids'
408 in_ty = envStackType env_ids stack
409 in_ty' = envStackType env_ids' stack'
411 mkFailExpr LambdaExpr in_ty' `thenDs` \ fail_expr ->
412 -- match the patterns against the top of the old stack
413 matchSimplys (map Var actual_ids) LambdaExpr pats core_expr fail_expr
414 `thenDs` \ match_code ->
415 -- match the old environment and stack against the input
416 matchEnvStack env_ids stack_ids match_code
417 `thenDs` \ select_code ->
418 returnDs (do_map_arrow ids in_ty in_ty' res_ty select_code core_body,
419 free_vars `minusVarSet` pat_vars)
421 dsCmd ids local_vars env_ids stack res_ty (HsPar cmd)
422 = dsLCmd ids local_vars env_ids stack res_ty cmd
424 -- A, xs |- e :: Bool
425 -- A | xs1 |- c1 :: [ts] t
426 -- A | xs2 |- c2 :: [ts] t
427 -- ----------------------------------------
428 -- A | xs |- if e then c1 else c2 :: [ts] t
430 -- ---> arr (\ ((xs)*ts) ->
431 -- if e then Left ((xs1)*ts) else Right ((xs2)*ts)) >>>
434 dsCmd ids local_vars env_ids stack res_ty (HsIf cond then_cmd else_cmd)
435 = dsLExpr cond `thenDs` \ core_cond ->
436 dsfixCmd ids local_vars stack res_ty then_cmd
437 `thenDs` \ (core_then, fvs_then, then_ids) ->
438 dsfixCmd ids local_vars stack res_ty else_cmd
439 `thenDs` \ (core_else, fvs_else, else_ids) ->
440 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
441 dsLookupTyCon eitherTyConName `thenDs` \ either_con ->
442 dsLookupDataCon leftDataConName `thenDs` \ left_con ->
443 dsLookupDataCon rightDataConName `thenDs` \ right_con ->
445 left_expr ty1 ty2 e = mkConApp left_con [Type ty1, Type ty2, e]
446 right_expr ty1 ty2 e = mkConApp right_con [Type ty1, Type ty2, e]
448 in_ty = envStackType env_ids stack
449 then_ty = envStackType then_ids stack
450 else_ty = envStackType else_ids stack
451 sum_ty = mkTyConApp either_con [then_ty, else_ty]
452 fvs_cond = exprFreeVars core_cond `intersectVarSet` local_vars
454 matchEnvStack env_ids stack_ids
455 (mkIfThenElse core_cond
456 (left_expr then_ty else_ty (buildEnvStack then_ids stack_ids))
457 (right_expr then_ty else_ty (buildEnvStack else_ids stack_ids)))
458 `thenDs` \ core_if ->
459 returnDs(do_map_arrow ids in_ty sum_ty res_ty
461 (do_choice ids then_ty else_ty res_ty core_then core_else),
462 fvs_cond `unionVarSet` fvs_then `unionVarSet` fvs_else)
465 Case commands are treated in much the same way as if commands
466 (see above) except that there are more alternatives. For example
468 case e of { p1 -> c1; p2 -> c2; p3 -> c3 }
472 arr (\ ((xs)*ts) -> case e of
473 p1 -> (Left (Left (xs1)*ts))
474 p2 -> Left ((Right (xs2)*ts))
475 p3 -> Right ((xs3)*ts)) >>>
478 The idea is to extract the commands from the case, build a balanced tree
479 of choices, and replace the commands with expressions that build tagged
480 tuples, obtaining a case expression that can be desugared normally.
481 To build all this, we use quadruples decribing segments of the list of
482 case bodies, containing the following fields:
483 1. an IdSet containing the environment variables free in the case bodies
484 2. a list of expressions of the form (Left|Right)* ((xs)*ts), to be put
485 into the case replacing the commands
486 3. a sum type that is the common type of these expressions, and also the
487 input type of the arrow
488 4. a CoreExpr for an arrow built by combining the translated command
492 dsCmd ids local_vars env_ids stack res_ty (HsCase exp matches)
493 = dsLExpr exp `thenDs` \ core_exp ->
494 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
496 -- Extract and desugar the leaf commands in the case, building tuple
497 -- expressions that will (after tagging) replace these leaves
500 leaves = concatMap leavesMatch matches
501 make_branch (leaf, bound_vars)
502 = dsfixCmd ids (local_vars `unionVarSet` bound_vars) stack res_ty leaf
503 `thenDs` \ (core_leaf, fvs, leaf_ids) ->
504 returnDs (fvs `minusVarSet` bound_vars,
505 [noLoc $ mkHsEnvStackExpr leaf_ids stack_ids],
506 envStackType leaf_ids stack,
509 mappM make_branch leaves `thenDs` \ branches ->
510 dsLookupTyCon eitherTyConName `thenDs` \ either_con ->
511 dsLookupDataCon leftDataConName `thenDs` \ left_con ->
512 dsLookupDataCon rightDataConName `thenDs` \ right_con ->
514 left_id = nlHsVar (dataConWrapId left_con)
515 right_id = nlHsVar (dataConWrapId right_con)
516 left_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ TyApp left_id [ty1, ty2]) e
517 right_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ TyApp right_id [ty1, ty2]) e
519 -- Prefix each tuple with a distinct series of Left's and Right's,
520 -- in a balanced way, keeping track of the types.
522 merge_branches (fvs1, builds1, in_ty1, core_exp1)
523 (fvs2, builds2, in_ty2, core_exp2)
524 = (fvs1 `unionVarSet` fvs2,
525 map (left_expr in_ty1 in_ty2) builds1 ++
526 map (right_expr in_ty1 in_ty2) builds2,
527 mkTyConApp either_con [in_ty1, in_ty2],
528 do_choice ids in_ty1 in_ty2 res_ty core_exp1 core_exp2)
529 (fvs_alts, leaves', sum_ty, core_choices)
530 = foldb merge_branches branches
532 -- Replace the commands in the case with these tagged tuples,
533 -- yielding a HsExpr Id we can feed to dsExpr.
535 (_, matches') = mapAccumL (replaceLeavesMatch res_ty) leaves' matches
536 in_ty = envStackType env_ids stack
537 fvs_exp = exprFreeVars core_exp `intersectVarSet` local_vars
539 dsExpr (HsCase exp matches') `thenDs` \ core_body ->
540 matchEnvStack env_ids stack_ids core_body
541 `thenDs` \ core_matches ->
542 returnDs(do_map_arrow ids in_ty sum_ty res_ty core_matches core_choices,
543 fvs_exp `unionVarSet` fvs_alts)
545 -- A | ys |- c :: [ts] t
546 -- ----------------------------------
547 -- A | xs |- let binds in c :: [ts] t
549 -- ---> arr (\ ((xs)*ts) -> let binds in ((ys)*ts)) >>> c
551 dsCmd ids local_vars env_ids stack res_ty (HsLet binds body)
553 defined_vars = mkVarSet (map unLoc (collectGroupBinders binds))
554 local_vars' = local_vars `unionVarSet` defined_vars
556 dsfixCmd ids local_vars' stack res_ty body
557 `thenDs` \ (core_body, free_vars, env_ids') ->
558 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
559 -- build a new environment, plus the stack, using the let bindings
560 dsLet binds (buildEnvStack env_ids' stack_ids)
561 `thenDs` \ core_binds ->
562 -- match the old environment and stack against the input
563 matchEnvStack env_ids stack_ids core_binds
564 `thenDs` \ core_map ->
565 returnDs (do_map_arrow ids
566 (envStackType env_ids stack)
567 (envStackType env_ids' stack)
571 exprFreeVars core_binds `intersectVarSet` local_vars)
573 dsCmd ids local_vars env_ids [] res_ty (HsDo _ctxt stmts _ _)
574 = dsCmdDo ids local_vars env_ids res_ty stmts
576 -- A |- e :: forall e. a1 (e*ts1) t1 -> ... an (e*tsn) tn -> a (e*ts) t
577 -- A | xs |- ci :: [tsi] ti
578 -- -----------------------------------
579 -- A | xs |- (|e c1 ... cn|) :: [ts] t ---> e [t_xs] c1 ... cn
581 dsCmd _ids local_vars env_ids _stack _res_ty (HsArrForm op _ args)
583 env_ty = mkTupleType env_ids
585 dsLExpr op `thenDs` \ core_op ->
586 mapAndUnzipDs (dsTrimCmdArg local_vars env_ids) args
587 `thenDs` \ (core_args, fv_sets) ->
588 returnDs (mkApps (App core_op (Type env_ty)) core_args,
589 unionVarSets fv_sets)
591 -- A | ys |- c :: [ts] t (ys <= xs)
592 -- ---------------------
593 -- A | xs |- c :: [ts] t ---> arr_ts (\ (xs) -> (ys)) >>> c
596 :: IdSet -- set of local vars available to this command
597 -> [Id] -- list of vars in the input to this command
598 -> LHsCmdTop Id -- command argument to desugar
599 -> DsM (CoreExpr, -- desugared expression
600 IdSet) -- set of local vars that occur free
601 dsTrimCmdArg local_vars env_ids (L _ (HsCmdTop cmd stack cmd_ty ids))
602 = mkCmdEnv ids `thenDs` \ meth_ids ->
603 dsfixCmd meth_ids local_vars stack cmd_ty cmd
604 `thenDs` \ (core_cmd, free_vars, env_ids') ->
605 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
606 matchEnvStack env_ids stack_ids (buildEnvStack env_ids' stack_ids)
607 `thenDs` \ trim_code ->
609 in_ty = envStackType env_ids stack
610 in_ty' = envStackType env_ids' stack
611 arg_code = if env_ids' == env_ids then core_cmd else
612 do_map_arrow meth_ids in_ty in_ty' cmd_ty trim_code core_cmd
614 returnDs (bindCmdEnv meth_ids arg_code, free_vars)
616 -- Given A | xs |- c :: [ts] t, builds c with xs fed back.
617 -- Typically needs to be prefixed with arr (\p -> ((xs)*ts))
620 :: DsCmdEnv -- arrow combinators
621 -> IdSet -- set of local vars available to this command
622 -> [Type] -- type of the stack
623 -> Type -- return type of the command
624 -> LHsCmd Id -- command to desugar
625 -> DsM (CoreExpr, -- desugared expression
626 IdSet, -- set of local vars that occur free
627 [Id]) -- set as a list, fed back
628 dsfixCmd ids local_vars stack cmd_ty cmd
629 = fixDs (\ ~(_,_,env_ids') ->
630 dsLCmd ids local_vars env_ids' stack cmd_ty cmd
631 `thenDs` \ (core_cmd, free_vars) ->
632 returnDs (core_cmd, free_vars, varSetElems free_vars))
636 Translation of command judgements of the form
638 A | xs |- do { ss } :: [] t
642 dsCmdDo :: DsCmdEnv -- arrow combinators
643 -> IdSet -- set of local vars available to this statement
644 -> [Id] -- list of vars in the input to this statement
645 -- This is typically fed back,
646 -- so don't pull on it too early
647 -> Type -- return type of the statement
648 -> [LStmt Id] -- statements to desugar
649 -> DsM (CoreExpr, -- desugared expression
650 IdSet) -- set of local vars that occur free
652 -- A | xs |- c :: [] t
653 -- --------------------------
654 -- A | xs |- do { c } :: [] t
656 dsCmdDo ids local_vars env_ids res_ty [L _ (ResultStmt cmd)]
657 = dsLCmd ids local_vars env_ids [] res_ty cmd
659 dsCmdDo ids local_vars env_ids res_ty (stmt:stmts)
661 bound_vars = mkVarSet (map unLoc (collectLStmtBinders stmt))
662 local_vars' = local_vars `unionVarSet` bound_vars
664 fixDs (\ ~(_,_,env_ids') ->
665 dsCmdDo ids local_vars' env_ids' res_ty stmts
666 `thenDs` \ (core_stmts, fv_stmts) ->
667 returnDs (core_stmts, fv_stmts, varSetElems fv_stmts))
668 `thenDs` \ (core_stmts, fv_stmts, env_ids') ->
669 dsCmdLStmt ids local_vars env_ids env_ids' stmt
670 `thenDs` \ (core_stmt, fv_stmt) ->
671 returnDs (do_compose ids
672 (mkTupleType env_ids)
673 (mkTupleType env_ids')
680 A statement maps one local environment to another, and is represented
681 as an arrow from one tuple type to another. A statement sequence is
682 translated to a composition of such arrows.
684 dsCmdLStmt ids local_vars env_ids out_ids cmd
685 = dsCmdStmt ids local_vars env_ids out_ids (unLoc cmd)
688 :: DsCmdEnv -- arrow combinators
689 -> IdSet -- set of local vars available to this statement
690 -> [Id] -- list of vars in the input to this statement
691 -- This is typically fed back,
692 -- so don't pull on it too early
693 -> [Id] -- list of vars in the output of this statement
694 -> Stmt Id -- statement to desugar
695 -> DsM (CoreExpr, -- desugared expression
696 IdSet) -- set of local vars that occur free
698 -- A | xs1 |- c :: [] t
699 -- A | xs' |- do { ss } :: [] t'
700 -- ------------------------------
701 -- A | xs |- do { c; ss } :: [] t'
703 -- ---> arr (\ (xs) -> ((xs1),(xs'))) >>> first c >>>
706 dsCmdStmt ids local_vars env_ids out_ids (ExprStmt cmd c_ty)
707 = dsfixCmd ids local_vars [] c_ty cmd
708 `thenDs` \ (core_cmd, fv_cmd, env_ids1) ->
709 matchEnvStack env_ids []
710 (mkCorePairExpr (mkTupleExpr env_ids1) (mkTupleExpr out_ids))
711 `thenDs` \ core_mux ->
713 in_ty = mkTupleType env_ids
714 in_ty1 = mkTupleType env_ids1
715 out_ty = mkTupleType out_ids
716 before_c_ty = mkCorePairTy in_ty1 out_ty
717 after_c_ty = mkCorePairTy c_ty out_ty
719 mkSndExpr c_ty out_ty `thenDs` \ snd_fn ->
720 returnDs (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
721 do_compose ids before_c_ty after_c_ty out_ty
722 (do_first ids in_ty1 c_ty out_ty core_cmd) $
723 do_arr ids after_c_ty out_ty snd_fn,
724 extendVarSetList fv_cmd out_ids)
727 -- A | xs1 |- c :: [] t
728 -- A | xs' |- do { ss } :: [] t' xs2 = xs' - defs(p)
729 -- -----------------------------------
730 -- A | xs |- do { p <- c; ss } :: [] t'
732 -- ---> arr (\ (xs) -> ((xs1),(xs2))) >>> first c >>>
733 -- arr (\ (p, (xs2)) -> (xs')) >>> ss
735 -- It would be simpler and more consistent to do this using second,
736 -- but that's likely to be defined in terms of first.
738 dsCmdStmt ids local_vars env_ids out_ids (BindStmt pat cmd)
739 = dsfixCmd ids local_vars [] (hsPatType pat) cmd
740 `thenDs` \ (core_cmd, fv_cmd, env_ids1) ->
742 pat_ty = hsPatType pat
743 pat_vars = mkVarSet (collectPatBinders pat)
744 env_ids2 = varSetElems (mkVarSet out_ids `minusVarSet` pat_vars)
745 env_ty2 = mkTupleType env_ids2
748 -- multiplexing function
749 -- \ (xs) -> ((xs1),(xs2))
751 matchEnvStack env_ids []
752 (mkCorePairExpr (mkTupleExpr env_ids1) (mkTupleExpr env_ids2))
753 `thenDs` \ core_mux ->
755 -- projection function
756 -- \ (p, (xs2)) -> (zs)
758 selectMatchVarL pat `thenDs` \ pat_id ->
759 newSysLocalDs env_ty2 `thenDs` \ env_id ->
760 newUniqueSupply `thenDs` \ uniqs ->
762 after_c_ty = mkCorePairTy pat_ty env_ty2
763 out_ty = mkTupleType out_ids
764 body_expr = coreCaseTuple uniqs env_id env_ids2 (mkTupleExpr out_ids)
766 mkFailExpr (StmtCtxt DoExpr) out_ty `thenDs` \ fail_expr ->
767 matchSimply (Var pat_id) (StmtCtxt DoExpr) pat body_expr fail_expr
768 `thenDs` \ match_code ->
769 newSysLocalDs after_c_ty `thenDs` \ pair_id ->
771 proj_expr = Lam pair_id (coreCasePair pair_id pat_id env_id match_code)
774 -- put it all together
776 in_ty = mkTupleType env_ids
777 in_ty1 = mkTupleType env_ids1
778 in_ty2 = mkTupleType env_ids2
779 before_c_ty = mkCorePairTy in_ty1 in_ty2
781 returnDs (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
782 do_compose ids before_c_ty after_c_ty out_ty
783 (do_first ids in_ty1 pat_ty in_ty2 core_cmd) $
784 do_arr ids after_c_ty out_ty proj_expr,
785 fv_cmd `unionVarSet` (mkVarSet out_ids `minusVarSet` pat_vars))
787 -- A | xs' |- do { ss } :: [] t
788 -- --------------------------------------
789 -- A | xs |- do { let binds; ss } :: [] t
791 -- ---> arr (\ (xs) -> let binds in (xs')) >>> ss
793 dsCmdStmt ids local_vars env_ids out_ids (LetStmt binds)
794 -- build a new environment using the let bindings
795 = dsLet binds (mkTupleExpr out_ids) `thenDs` \ core_binds ->
796 -- match the old environment against the input
797 matchEnvStack env_ids [] core_binds `thenDs` \ core_map ->
799 (mkTupleType env_ids)
800 (mkTupleType out_ids)
802 exprFreeVars core_binds `intersectVarSet` local_vars)
804 -- A | ys |- do { ss; returnA -< ((xs1), (ys2)) } :: [] ...
805 -- A | xs' |- do { ss' } :: [] t
806 -- ------------------------------------
807 -- A | xs |- do { rec ss; ss' } :: [] t
809 -- xs1 = xs' /\ defs(ss)
810 -- xs2 = xs' - defs(ss)
811 -- ys1 = ys - defs(ss)
812 -- ys2 = ys /\ defs(ss)
814 -- ---> arr (\(xs) -> ((ys1),(xs2))) >>>
815 -- first (loop (arr (\((ys1),~(ys2)) -> (ys)) >>> ss)) >>>
816 -- arr (\((xs1),(xs2)) -> (xs')) >>> ss'
818 dsCmdStmt ids local_vars env_ids out_ids (RecStmt stmts later_ids rec_ids rhss)
820 env2_id_set = mkVarSet out_ids `minusVarSet` mkVarSet later_ids
821 env2_ids = varSetElems env2_id_set
822 env2_ty = mkTupleType env2_ids
825 -- post_loop_fn = \((later_ids),(env2_ids)) -> (out_ids)
827 newUniqueSupply `thenDs` \ uniqs ->
828 newSysLocalDs env2_ty `thenDs` \ env2_id ->
830 later_ty = mkTupleType later_ids
831 post_pair_ty = mkCorePairTy later_ty env2_ty
832 post_loop_body = coreCaseTuple uniqs env2_id env2_ids (mkTupleExpr out_ids)
834 matchEnvStack later_ids [env2_id] post_loop_body
835 `thenDs` \ post_loop_fn ->
839 dsRecCmd ids local_vars stmts later_ids rec_ids rhss
840 `thenDs` \ (core_loop, env1_id_set, env1_ids) ->
842 -- pre_loop_fn = \(env_ids) -> ((env1_ids),(env2_ids))
845 env1_ty = mkTupleType env1_ids
846 pre_pair_ty = mkCorePairTy env1_ty env2_ty
847 pre_loop_body = mkCorePairExpr (mkTupleExpr env1_ids)
848 (mkTupleExpr env2_ids)
851 matchEnvStack env_ids [] pre_loop_body
852 `thenDs` \ pre_loop_fn ->
854 -- arr pre_loop_fn >>> first (loop (...)) >>> arr post_loop_fn
857 env_ty = mkTupleType env_ids
858 out_ty = mkTupleType out_ids
859 core_body = do_map_arrow ids env_ty pre_pair_ty out_ty
861 (do_compose ids pre_pair_ty post_pair_ty out_ty
862 (do_first ids env1_ty later_ty env2_ty
864 (do_arr ids post_pair_ty out_ty
867 returnDs (core_body, env1_id_set `unionVarSet` env2_id_set)
869 -- loop (arr (\ ((env1_ids), ~(rec_ids)) -> (env_ids)) >>>
871 -- arr (\ (out_ids) -> ((later_ids),(rhss))) >>>
873 dsRecCmd ids local_vars stmts later_ids rec_ids rhss
875 rec_id_set = mkVarSet rec_ids
876 out_ids = varSetElems (mkVarSet later_ids `unionVarSet` rec_id_set)
877 out_ty = mkTupleType out_ids
878 local_vars' = local_vars `unionVarSet` rec_id_set
881 -- mk_pair_fn = \ (out_ids) -> ((later_ids),(rhss))
883 mappM dsLExpr rhss `thenDs` \ core_rhss ->
885 later_tuple = mkTupleExpr later_ids
886 later_ty = mkTupleType later_ids
887 rec_tuple = mkBigCoreTup core_rhss
888 rec_ty = mkTupleType rec_ids
889 out_pair = mkCorePairExpr later_tuple rec_tuple
890 out_pair_ty = mkCorePairTy later_ty rec_ty
892 matchEnvStack out_ids [] out_pair
893 `thenDs` \ mk_pair_fn ->
897 dsfixCmdStmts ids local_vars' out_ids stmts
898 `thenDs` \ (core_stmts, fv_stmts, env_ids) ->
900 -- squash_pair_fn = \ ((env1_ids), ~(rec_ids)) -> (env_ids)
902 newSysLocalDs rec_ty `thenDs` \ rec_id ->
904 env1_id_set = fv_stmts `minusVarSet` rec_id_set
905 env1_ids = varSetElems env1_id_set
906 env1_ty = mkTupleType env1_ids
907 in_pair_ty = mkCorePairTy env1_ty rec_ty
908 core_body = mkBigCoreTup (map selectVar env_ids)
911 | v `elemVarSet` rec_id_set
912 = mkTupleSelector rec_ids v rec_id (Var rec_id)
915 matchEnvStack env1_ids [rec_id] core_body
916 `thenDs` \ squash_pair_fn ->
918 -- loop (arr squash_pair_fn >>> ss >>> arr mk_pair_fn)
921 env_ty = mkTupleType env_ids
922 core_loop = do_loop ids env1_ty later_ty rec_ty
923 (do_map_arrow ids in_pair_ty env_ty out_pair_ty
925 (do_compose ids env_ty out_ty out_pair_ty
927 (do_arr ids out_ty out_pair_ty mk_pair_fn)))
929 returnDs (core_loop, env1_id_set, env1_ids)
932 A sequence of statements (as in a rec) is desugared to an arrow between
937 :: DsCmdEnv -- arrow combinators
938 -> IdSet -- set of local vars available to this statement
939 -> [Id] -- output vars of these statements
940 -> [LStmt Id] -- statements to desugar
941 -> DsM (CoreExpr, -- desugared expression
942 IdSet, -- set of local vars that occur free
945 dsfixCmdStmts ids local_vars out_ids stmts
946 = fixDs (\ ~(_,_,env_ids) ->
947 dsCmdStmts ids local_vars env_ids out_ids stmts
948 `thenDs` \ (core_stmts, fv_stmts) ->
949 returnDs (core_stmts, fv_stmts, varSetElems fv_stmts))
952 :: DsCmdEnv -- arrow combinators
953 -> IdSet -- set of local vars available to this statement
954 -> [Id] -- list of vars in the input to these statements
955 -> [Id] -- output vars of these statements
956 -> [LStmt Id] -- statements to desugar
957 -> DsM (CoreExpr, -- desugared expression
958 IdSet) -- set of local vars that occur free
960 dsCmdStmts ids local_vars env_ids out_ids [stmt]
961 = dsCmdLStmt ids local_vars env_ids out_ids stmt
963 dsCmdStmts ids local_vars env_ids out_ids (stmt:stmts)
965 bound_vars = mkVarSet (map unLoc (collectLStmtBinders stmt))
966 local_vars' = local_vars `unionVarSet` bound_vars
968 dsfixCmdStmts ids local_vars' out_ids stmts
969 `thenDs` \ (core_stmts, fv_stmts, env_ids') ->
970 dsCmdLStmt ids local_vars env_ids env_ids' stmt
971 `thenDs` \ (core_stmt, fv_stmt) ->
972 returnDs (do_compose ids
973 (mkTupleType env_ids)
974 (mkTupleType env_ids')
975 (mkTupleType out_ids)
982 Match a list of expressions against a list of patterns, left-to-right.
985 matchSimplys :: [CoreExpr] -- Scrutinees
986 -> HsMatchContext Name -- Match kind
987 -> [LPat Id] -- Patterns they should match
988 -> CoreExpr -- Return this if they all match
989 -> CoreExpr -- Return this if they don't
991 matchSimplys [] _ctxt [] result_expr _fail_expr = returnDs result_expr
992 matchSimplys (exp:exps) ctxt (pat:pats) result_expr fail_expr
993 = matchSimplys exps ctxt pats result_expr fail_expr
994 `thenDs` \ match_code ->
995 matchSimply exp ctxt pat match_code fail_expr
998 List of leaf expressions, with set of variables bound in each
1001 leavesMatch :: LMatch Id -> [(LHsExpr Id, IdSet)]
1002 leavesMatch (L _ (Match pats _ (GRHSs grhss binds _ty)))
1004 defined_vars = mkVarSet (collectPatsBinders pats)
1006 mkVarSet (map unLoc (collectGroupBinders binds))
1009 mkVarSet (map unLoc (collectStmtsBinders stmts))
1010 `unionVarSet` defined_vars)
1011 | L _ (GRHS stmts) <- grhss,
1012 let L _ (ResultStmt expr) = last stmts]
1015 Replace the leaf commands in a match
1019 :: Type -- new result type
1020 -> [LHsExpr Id] -- replacement leaf expressions of that type
1021 -> LMatch Id -- the matches of a case command
1022 -> ([LHsExpr Id],-- remaining leaf expressions
1023 LMatch Id) -- updated match
1024 replaceLeavesMatch res_ty leaves (L loc (Match pat mt (GRHSs grhss binds _ty)))
1026 (leaves', grhss') = mapAccumL replaceLeavesGRHS leaves grhss
1028 (leaves', L loc (Match pat mt (GRHSs grhss' binds res_ty)))
1031 :: [LHsExpr Id] -- replacement leaf expressions of that type
1032 -> LGRHS Id -- rhss of a case command
1033 -> ([LHsExpr Id],-- remaining leaf expressions
1034 LGRHS Id) -- updated GRHS
1035 replaceLeavesGRHS (leaf:leaves) (L loc (GRHS stmts))
1036 = (leaves, L loc (GRHS (init stmts ++ [L (getLoc leaf) (ResultStmt leaf)])))
1039 Balanced fold of a non-empty list.
1042 foldb :: (a -> a -> a) -> [a] -> a
1043 foldb _ [] = error "foldb of empty list"
1045 foldb f xs = foldb f (fold_pairs xs)
1048 fold_pairs [x] = [x]
1049 fold_pairs (x1:x2:xs) = f x1 x2:fold_pairs xs