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
294 -- ---------------------------
295 -- A | xs |- f -< arg :: [] t' ---> arr (\ (xs) -> arg) >>> f
297 dsCmd ids local_vars env_ids [] res_ty
298 (HsArrApp arrow arg arrow_ty HsFirstOrderApp _)
300 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
301 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
302 env_ty = mkTupleType env_ids
304 dsLExpr arrow `thenDs` \ core_arrow ->
305 dsLExpr arg `thenDs` \ core_arg ->
306 matchEnvStack env_ids [] core_arg `thenDs` \ core_make_arg ->
307 returnDs (do_map_arrow ids env_ty arg_ty res_ty
310 exprFreeVars core_arg `intersectVarSet` local_vars)
312 -- A, xs |- f :: a t t'
314 -- ---------------------------
315 -- A | xs |- f -<< arg :: [] t' ---> arr (\ (xs) -> (f,arg)) >>> app
317 dsCmd ids local_vars env_ids [] res_ty
318 (HsArrApp arrow arg arrow_ty HsHigherOrderApp _)
320 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
321 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
322 env_ty = mkTupleType env_ids
324 dsLExpr arrow `thenDs` \ core_arrow ->
325 dsLExpr arg `thenDs` \ core_arg ->
326 matchEnvStack env_ids [] (mkCorePairExpr core_arrow core_arg)
327 `thenDs` \ core_make_pair ->
328 returnDs (do_map_arrow ids env_ty (mkCorePairTy arrow_ty arg_ty) res_ty
330 (do_app ids arg_ty res_ty),
331 (exprFreeVars core_arrow `unionVarSet` exprFreeVars core_arg)
332 `intersectVarSet` local_vars)
334 -- A | ys |- c :: [t:ts] t'
336 -- ------------------------
337 -- A | xs |- c e :: [ts] t'
339 -- ---> arr (\ ((xs)*ts) -> let z = e in (((ys),z)*ts)) >>> c
341 dsCmd ids local_vars env_ids stack res_ty (HsApp cmd arg)
342 = dsLExpr arg `thenDs` \ core_arg ->
344 arg_ty = exprType core_arg
345 stack' = arg_ty:stack
347 dsfixCmd ids local_vars stack' res_ty cmd
348 `thenDs` \ (core_cmd, free_vars, env_ids') ->
349 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
350 newSysLocalDs arg_ty `thenDs` \ arg_id ->
351 -- push the argument expression onto the stack
353 core_body = bindNonRec arg_id core_arg
354 (buildEnvStack env_ids' (arg_id:stack_ids))
356 -- match the environment and stack against the input
357 matchEnvStack env_ids stack_ids core_body
358 `thenDs` \ core_map ->
359 returnDs (do_map_arrow ids
360 (envStackType env_ids stack)
361 (envStackType env_ids' stack')
365 (exprFreeVars core_arg `intersectVarSet` local_vars)
366 `unionVarSet` free_vars)
368 -- A | ys |- c :: [ts] t'
369 -- -----------------------------------------------
370 -- A | xs |- \ p1 ... pk -> c :: [t1:...:tk:ts] t'
372 -- ---> arr (\ ((((xs), p1), ... pk)*ts) -> ((ys)*ts)) >>> c
374 dsCmd ids local_vars env_ids stack res_ty
375 (HsLam (L _ (Match pats _ (GRHSs [L _ (GRHS [L _ (ResultStmt body)])] _ _cmd_ty))))
377 pat_vars = mkVarSet (collectPatsBinders pats)
378 local_vars' = local_vars `unionVarSet` pat_vars
379 stack' = drop (length pats) stack
381 dsfixCmd ids local_vars' stack' res_ty body
382 `thenDs` \ (core_body, free_vars, env_ids') ->
383 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
385 -- the expression is built from the inside out, so the actions
386 -- are presented in reverse order
389 (actual_ids, stack_ids') = splitAt (length pats) stack_ids
390 -- build a new environment, plus what's left of the stack
391 core_expr = buildEnvStack env_ids' stack_ids'
392 in_ty = envStackType env_ids stack
393 in_ty' = envStackType env_ids' stack'
395 mkFailExpr LambdaExpr in_ty' `thenDs` \ fail_expr ->
396 -- match the patterns against the top of the old stack
397 matchSimplys (map Var actual_ids) LambdaExpr pats core_expr fail_expr
398 `thenDs` \ match_code ->
399 -- match the old environment and stack against the input
400 matchEnvStack env_ids stack_ids match_code
401 `thenDs` \ select_code ->
402 returnDs (do_map_arrow ids in_ty in_ty' res_ty select_code core_body,
403 free_vars `minusVarSet` pat_vars)
405 dsCmd ids local_vars env_ids stack res_ty (HsPar cmd)
406 = dsLCmd ids local_vars env_ids stack res_ty cmd
408 -- A, xs |- e :: Bool
409 -- A | xs1 |- c1 :: [ts] t
410 -- A | xs2 |- c2 :: [ts] t
411 -- ----------------------------------------
412 -- A | xs |- if e then c1 else c2 :: [ts] t
414 -- ---> arr (\ ((xs)*ts) ->
415 -- if e then Left ((xs1)*ts) else Right ((xs2)*ts)) >>>
418 dsCmd ids local_vars env_ids stack res_ty (HsIf cond then_cmd else_cmd)
419 = dsLExpr cond `thenDs` \ core_cond ->
420 dsfixCmd ids local_vars stack res_ty then_cmd
421 `thenDs` \ (core_then, fvs_then, then_ids) ->
422 dsfixCmd ids local_vars stack res_ty else_cmd
423 `thenDs` \ (core_else, fvs_else, else_ids) ->
424 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
425 dsLookupTyCon eitherTyConName `thenDs` \ either_con ->
426 dsLookupDataCon leftDataConName `thenDs` \ left_con ->
427 dsLookupDataCon rightDataConName `thenDs` \ right_con ->
429 left_expr ty1 ty2 e = mkConApp left_con [Type ty1, Type ty2, e]
430 right_expr ty1 ty2 e = mkConApp right_con [Type ty1, Type ty2, e]
432 in_ty = envStackType env_ids stack
433 then_ty = envStackType then_ids stack
434 else_ty = envStackType else_ids stack
435 sum_ty = mkTyConApp either_con [then_ty, else_ty]
436 fvs_cond = exprFreeVars core_cond `intersectVarSet` local_vars
438 matchEnvStack env_ids stack_ids
439 (mkIfThenElse core_cond
440 (left_expr then_ty else_ty (buildEnvStack then_ids stack_ids))
441 (right_expr then_ty else_ty (buildEnvStack else_ids stack_ids)))
442 `thenDs` \ core_if ->
443 returnDs(do_map_arrow ids in_ty sum_ty res_ty
445 (do_choice ids then_ty else_ty res_ty core_then core_else),
446 fvs_cond `unionVarSet` fvs_then `unionVarSet` fvs_else)
449 Case commands are treated in much the same way as if commands
450 (see above) except that there are more alternatives. For example
452 case e of { p1 -> c1; p2 -> c2; p3 -> c3 }
456 arr (\ ((xs)*ts) -> case e of
457 p1 -> (Left (Left (xs1)*ts))
458 p2 -> Left ((Right (xs2)*ts))
459 p3 -> Right ((xs3)*ts)) >>>
462 The idea is to extract the commands from the case, build a balanced tree
463 of choices, and replace the commands with expressions that build tagged
464 tuples, obtaining a case expression that can be desugared normally.
465 To build all this, we use quadruples decribing segments of the list of
466 case bodies, containing the following fields:
467 1. an IdSet containing the environment variables free in the case bodies
468 2. a list of expressions of the form (Left|Right)* ((xs)*ts), to be put
469 into the case replacing the commands
470 3. a sum type that is the common type of these expressions, and also the
471 input type of the arrow
472 4. a CoreExpr for an arrow built by combining the translated command
476 dsCmd ids local_vars env_ids stack res_ty (HsCase exp matches)
477 = dsLExpr exp `thenDs` \ core_exp ->
478 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
480 -- Extract and desugar the leaf commands in the case, building tuple
481 -- expressions that will (after tagging) replace these leaves
484 leaves = concatMap leavesMatch matches
485 make_branch (leaf, bound_vars)
486 = dsfixCmd ids (local_vars `unionVarSet` bound_vars) stack res_ty leaf
487 `thenDs` \ (core_leaf, fvs, leaf_ids) ->
488 returnDs (fvs `minusVarSet` bound_vars,
489 [noLoc $ mkHsEnvStackExpr leaf_ids stack_ids],
490 envStackType leaf_ids stack,
493 mappM make_branch leaves `thenDs` \ branches ->
494 dsLookupTyCon eitherTyConName `thenDs` \ either_con ->
495 dsLookupDataCon leftDataConName `thenDs` \ left_con ->
496 dsLookupDataCon rightDataConName `thenDs` \ right_con ->
498 left_id = nlHsVar (dataConWrapId left_con)
499 right_id = nlHsVar (dataConWrapId right_con)
500 left_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ TyApp left_id [ty1, ty2]) e
501 right_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ TyApp right_id [ty1, ty2]) e
503 -- Prefix each tuple with a distinct series of Left's and Right's,
504 -- in a balanced way, keeping track of the types.
506 merge_branches (fvs1, builds1, in_ty1, core_exp1)
507 (fvs2, builds2, in_ty2, core_exp2)
508 = (fvs1 `unionVarSet` fvs2,
509 map (left_expr in_ty1 in_ty2) builds1 ++
510 map (right_expr in_ty1 in_ty2) builds2,
511 mkTyConApp either_con [in_ty1, in_ty2],
512 do_choice ids in_ty1 in_ty2 res_ty core_exp1 core_exp2)
513 (fvs_alts, leaves', sum_ty, core_choices)
514 = foldb merge_branches branches
516 -- Replace the commands in the case with these tagged tuples,
517 -- yielding a HsExpr Id we can feed to dsExpr.
519 (_, matches') = mapAccumL (replaceLeavesMatch res_ty) leaves' matches
520 in_ty = envStackType env_ids stack
521 fvs_exp = exprFreeVars core_exp `intersectVarSet` local_vars
523 dsExpr (HsCase exp matches') `thenDs` \ core_body ->
524 matchEnvStack env_ids stack_ids core_body
525 `thenDs` \ core_matches ->
526 returnDs(do_map_arrow ids in_ty sum_ty res_ty core_matches core_choices,
527 fvs_exp `unionVarSet` fvs_alts)
529 -- A | ys |- c :: [ts] t
530 -- ----------------------------------
531 -- A | xs |- let binds in c :: [ts] t
533 -- ---> arr (\ ((xs)*ts) -> let binds in ((ys)*ts)) >>> c
535 dsCmd ids local_vars env_ids stack res_ty (HsLet binds body)
537 defined_vars = mkVarSet (map unLoc (collectGroupBinders binds))
538 local_vars' = local_vars `unionVarSet` defined_vars
540 dsfixCmd ids local_vars' stack res_ty body
541 `thenDs` \ (core_body, free_vars, env_ids') ->
542 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
543 -- build a new environment, plus the stack, using the let bindings
544 dsLet binds (buildEnvStack env_ids' stack_ids)
545 `thenDs` \ core_binds ->
546 -- match the old environment and stack against the input
547 matchEnvStack env_ids stack_ids core_binds
548 `thenDs` \ core_map ->
549 returnDs (do_map_arrow ids
550 (envStackType env_ids stack)
551 (envStackType env_ids' stack)
555 exprFreeVars core_binds `intersectVarSet` local_vars)
557 dsCmd ids local_vars env_ids [] res_ty (HsDo _ctxt stmts _ _)
558 = dsCmdDo ids local_vars env_ids res_ty stmts
560 -- A |- e :: forall e. a1 (e*ts1) t1 -> ... an (e*tsn) tn -> a (e*ts) t
561 -- A | xs |- ci :: [tsi] ti
562 -- -----------------------------------
563 -- A | xs |- (|e c1 ... cn|) :: [ts] t ---> e [t_xs] c1 ... cn
565 dsCmd _ids local_vars env_ids _stack _res_ty (HsArrForm op _ args)
567 env_ty = mkTupleType env_ids
569 dsLExpr op `thenDs` \ core_op ->
570 mapAndUnzipDs (dsTrimCmdArg local_vars env_ids) args
571 `thenDs` \ (core_args, fv_sets) ->
572 returnDs (mkApps (App core_op (Type env_ty)) core_args,
573 unionVarSets fv_sets)
575 -- A | ys |- c :: [ts] t (ys <= xs)
576 -- ---------------------
577 -- A | xs |- c :: [ts] t ---> arr_ts (\ (xs) -> (ys)) >>> c
580 :: IdSet -- set of local vars available to this command
581 -> [Id] -- list of vars in the input to this command
582 -> LHsCmdTop Id -- command argument to desugar
583 -> DsM (CoreExpr, -- desugared expression
584 IdSet) -- set of local vars that occur free
585 dsTrimCmdArg local_vars env_ids (L _ (HsCmdTop cmd stack cmd_ty ids))
586 = mkCmdEnv ids `thenDs` \ meth_ids ->
587 dsfixCmd meth_ids local_vars stack cmd_ty cmd
588 `thenDs` \ (core_cmd, free_vars, env_ids') ->
589 mappM newSysLocalDs stack `thenDs` \ stack_ids ->
590 matchEnvStack env_ids stack_ids (buildEnvStack env_ids' stack_ids)
591 `thenDs` \ trim_code ->
593 in_ty = envStackType env_ids stack
594 in_ty' = envStackType env_ids' stack
595 arg_code = if env_ids' == env_ids then core_cmd else
596 do_map_arrow meth_ids in_ty in_ty' cmd_ty trim_code core_cmd
598 returnDs (bindCmdEnv meth_ids arg_code, free_vars)
600 -- Given A | xs |- c :: [ts] t, builds c with xs fed back.
601 -- Typically needs to be prefixed with arr (\p -> ((xs)*ts))
604 :: DsCmdEnv -- arrow combinators
605 -> IdSet -- set of local vars available to this command
606 -> [Type] -- type of the stack
607 -> Type -- return type of the command
608 -> LHsCmd Id -- command to desugar
609 -> DsM (CoreExpr, -- desugared expression
610 IdSet, -- set of local vars that occur free
611 [Id]) -- set as a list, fed back
612 dsfixCmd ids local_vars stack cmd_ty cmd
613 = fixDs (\ ~(_,_,env_ids') ->
614 dsLCmd ids local_vars env_ids' stack cmd_ty cmd
615 `thenDs` \ (core_cmd, free_vars) ->
616 returnDs (core_cmd, free_vars, varSetElems free_vars))
620 Translation of command judgements of the form
622 A | xs |- do { ss } :: [] t
626 dsCmdDo :: DsCmdEnv -- arrow combinators
627 -> IdSet -- set of local vars available to this statement
628 -> [Id] -- list of vars in the input to this statement
629 -- This is typically fed back,
630 -- so don't pull on it too early
631 -> Type -- return type of the statement
632 -> [LStmt Id] -- statements to desugar
633 -> DsM (CoreExpr, -- desugared expression
634 IdSet) -- set of local vars that occur free
636 -- A | xs |- c :: [] t
637 -- --------------------------
638 -- A | xs |- do { c } :: [] t
640 dsCmdDo ids local_vars env_ids res_ty [L _ (ResultStmt cmd)]
641 = dsLCmd ids local_vars env_ids [] res_ty cmd
643 dsCmdDo ids local_vars env_ids res_ty (stmt:stmts)
645 bound_vars = mkVarSet (map unLoc (collectLStmtBinders stmt))
646 local_vars' = local_vars `unionVarSet` bound_vars
648 fixDs (\ ~(_,_,env_ids') ->
649 dsCmdDo ids local_vars' env_ids' res_ty stmts
650 `thenDs` \ (core_stmts, fv_stmts) ->
651 returnDs (core_stmts, fv_stmts, varSetElems fv_stmts))
652 `thenDs` \ (core_stmts, fv_stmts, env_ids') ->
653 dsCmdLStmt ids local_vars env_ids env_ids' stmt
654 `thenDs` \ (core_stmt, fv_stmt) ->
655 returnDs (do_compose ids
656 (mkTupleType env_ids)
657 (mkTupleType env_ids')
664 A statement maps one local environment to another, and is represented
665 as an arrow from one tuple type to another. A statement sequence is
666 translated to a composition of such arrows.
668 dsCmdLStmt ids local_vars env_ids out_ids cmd
669 = dsCmdStmt ids local_vars env_ids out_ids (unLoc cmd)
672 :: DsCmdEnv -- arrow combinators
673 -> IdSet -- set of local vars available to this statement
674 -> [Id] -- list of vars in the input to this statement
675 -- This is typically fed back,
676 -- so don't pull on it too early
677 -> [Id] -- list of vars in the output of this statement
678 -> Stmt Id -- statement to desugar
679 -> DsM (CoreExpr, -- desugared expression
680 IdSet) -- set of local vars that occur free
682 -- A | xs1 |- c :: [] t
683 -- A | xs' |- do { ss } :: [] t'
684 -- ------------------------------
685 -- A | xs |- do { c; ss } :: [] t'
687 -- ---> arr (\ (xs) -> ((xs1),(xs'))) >>> first c >>>
690 dsCmdStmt ids local_vars env_ids out_ids (ExprStmt cmd c_ty)
691 = dsfixCmd ids local_vars [] c_ty cmd
692 `thenDs` \ (core_cmd, fv_cmd, env_ids1) ->
693 matchEnvStack env_ids []
694 (mkCorePairExpr (mkTupleExpr env_ids1) (mkTupleExpr out_ids))
695 `thenDs` \ core_mux ->
697 in_ty = mkTupleType env_ids
698 in_ty1 = mkTupleType env_ids1
699 out_ty = mkTupleType out_ids
700 before_c_ty = mkCorePairTy in_ty1 out_ty
701 after_c_ty = mkCorePairTy c_ty out_ty
703 mkSndExpr c_ty out_ty `thenDs` \ snd_fn ->
704 returnDs (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
705 do_compose ids before_c_ty after_c_ty out_ty
706 (do_first ids in_ty1 c_ty out_ty core_cmd) $
707 do_arr ids after_c_ty out_ty snd_fn,
708 extendVarSetList fv_cmd out_ids)
711 -- A | xs1 |- c :: [] t
712 -- A | xs' |- do { ss } :: [] t' xs2 = xs' - defs(p)
713 -- -----------------------------------
714 -- A | xs |- do { p <- c; ss } :: [] t'
716 -- ---> arr (\ (xs) -> ((xs1),(xs2))) >>> first c >>>
717 -- arr (\ (p, (xs2)) -> (xs')) >>> ss
719 -- It would be simpler and more consistent to do this using second,
720 -- but that's likely to be defined in terms of first.
722 dsCmdStmt ids local_vars env_ids out_ids (BindStmt pat cmd)
723 = dsfixCmd ids local_vars [] (hsPatType pat) cmd
724 `thenDs` \ (core_cmd, fv_cmd, env_ids1) ->
726 pat_ty = hsPatType pat
727 pat_vars = mkVarSet (collectPatBinders pat)
728 env_ids2 = varSetElems (mkVarSet out_ids `minusVarSet` pat_vars)
729 env_ty2 = mkTupleType env_ids2
732 -- multiplexing function
733 -- \ (xs) -> ((xs1),(xs2))
735 matchEnvStack env_ids []
736 (mkCorePairExpr (mkTupleExpr env_ids1) (mkTupleExpr env_ids2))
737 `thenDs` \ core_mux ->
739 -- projection function
740 -- \ (p, (xs2)) -> (zs)
742 selectMatchVarL pat `thenDs` \ pat_id ->
743 newSysLocalDs env_ty2 `thenDs` \ env_id ->
744 newUniqueSupply `thenDs` \ uniqs ->
746 after_c_ty = mkCorePairTy pat_ty env_ty2
747 out_ty = mkTupleType out_ids
748 body_expr = coreCaseTuple uniqs env_id env_ids2 (mkTupleExpr out_ids)
750 mkFailExpr (StmtCtxt DoExpr) out_ty `thenDs` \ fail_expr ->
751 matchSimply (Var pat_id) (StmtCtxt DoExpr) pat body_expr fail_expr
752 `thenDs` \ match_code ->
753 newSysLocalDs after_c_ty `thenDs` \ pair_id ->
755 proj_expr = Lam pair_id (coreCasePair pair_id pat_id env_id match_code)
758 -- put it all together
760 in_ty = mkTupleType env_ids
761 in_ty1 = mkTupleType env_ids1
762 in_ty2 = mkTupleType env_ids2
763 before_c_ty = mkCorePairTy in_ty1 in_ty2
765 returnDs (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
766 do_compose ids before_c_ty after_c_ty out_ty
767 (do_first ids in_ty1 pat_ty in_ty2 core_cmd) $
768 do_arr ids after_c_ty out_ty proj_expr,
769 fv_cmd `unionVarSet` (mkVarSet out_ids `minusVarSet` pat_vars))
771 -- A | xs' |- do { ss } :: [] t
772 -- --------------------------------------
773 -- A | xs |- do { let binds; ss } :: [] t
775 -- ---> arr (\ (xs) -> let binds in (xs')) >>> ss
777 dsCmdStmt ids local_vars env_ids out_ids (LetStmt binds)
778 -- build a new environment using the let bindings
779 = dsLet binds (mkTupleExpr out_ids) `thenDs` \ core_binds ->
780 -- match the old environment against the input
781 matchEnvStack env_ids [] core_binds `thenDs` \ core_map ->
783 (mkTupleType env_ids)
784 (mkTupleType out_ids)
786 exprFreeVars core_binds `intersectVarSet` local_vars)
788 -- A | ys |- do { ss; returnA -< ((xs1), (ys2)) } :: [] ...
789 -- A | xs' |- do { ss' } :: [] t
790 -- ------------------------------------
791 -- A | xs |- do { rec ss; ss' } :: [] t
793 -- xs1 = xs' /\ defs(ss)
794 -- xs2 = xs' - defs(ss)
795 -- ys1 = ys - defs(ss)
796 -- ys2 = ys /\ defs(ss)
798 -- ---> arr (\(xs) -> ((ys1),(xs2))) >>>
799 -- first (loop (arr (\((ys1),~(ys2)) -> (ys)) >>> ss)) >>>
800 -- arr (\((xs1),(xs2)) -> (xs')) >>> ss'
802 dsCmdStmt ids local_vars env_ids out_ids (RecStmt stmts later_ids rec_ids rhss)
804 env2_id_set = mkVarSet out_ids `minusVarSet` mkVarSet later_ids
805 env2_ids = varSetElems env2_id_set
806 env2_ty = mkTupleType env2_ids
809 -- post_loop_fn = \((later_ids),(env2_ids)) -> (out_ids)
811 newUniqueSupply `thenDs` \ uniqs ->
812 newSysLocalDs env2_ty `thenDs` \ env2_id ->
814 later_ty = mkTupleType later_ids
815 post_pair_ty = mkCorePairTy later_ty env2_ty
816 post_loop_body = coreCaseTuple uniqs env2_id env2_ids (mkTupleExpr out_ids)
818 matchEnvStack later_ids [env2_id] post_loop_body
819 `thenDs` \ post_loop_fn ->
823 dsRecCmd ids local_vars stmts later_ids rec_ids rhss
824 `thenDs` \ (core_loop, env1_id_set, env1_ids) ->
826 -- pre_loop_fn = \(env_ids) -> ((env1_ids),(env2_ids))
829 env1_ty = mkTupleType env1_ids
830 pre_pair_ty = mkCorePairTy env1_ty env2_ty
831 pre_loop_body = mkCorePairExpr (mkTupleExpr env1_ids)
832 (mkTupleExpr env2_ids)
835 matchEnvStack env_ids [] pre_loop_body
836 `thenDs` \ pre_loop_fn ->
838 -- arr pre_loop_fn >>> first (loop (...)) >>> arr post_loop_fn
841 env_ty = mkTupleType env_ids
842 out_ty = mkTupleType out_ids
843 core_body = do_map_arrow ids env_ty pre_pair_ty out_ty
845 (do_compose ids pre_pair_ty post_pair_ty out_ty
846 (do_first ids env1_ty later_ty env2_ty
848 (do_arr ids post_pair_ty out_ty
851 returnDs (core_body, env1_id_set `unionVarSet` env2_id_set)
853 -- loop (arr (\ ((env1_ids), ~(rec_ids)) -> (env_ids)) >>>
855 -- arr (\ (out_ids) -> ((later_ids),(rhss))) >>>
857 dsRecCmd ids local_vars stmts later_ids rec_ids rhss
859 rec_id_set = mkVarSet rec_ids
860 out_ids = varSetElems (mkVarSet later_ids `unionVarSet` rec_id_set)
861 out_ty = mkTupleType out_ids
862 local_vars' = local_vars `unionVarSet` rec_id_set
865 -- mk_pair_fn = \ (out_ids) -> ((later_ids),(rhss))
867 mappM dsLExpr rhss `thenDs` \ core_rhss ->
869 later_tuple = mkTupleExpr later_ids
870 later_ty = mkTupleType later_ids
871 rec_tuple = mkBigCoreTup core_rhss
872 rec_ty = mkTupleType rec_ids
873 out_pair = mkCorePairExpr later_tuple rec_tuple
874 out_pair_ty = mkCorePairTy later_ty rec_ty
876 matchEnvStack out_ids [] out_pair
877 `thenDs` \ mk_pair_fn ->
881 dsfixCmdStmts ids local_vars' out_ids stmts
882 `thenDs` \ (core_stmts, fv_stmts, env_ids) ->
884 -- squash_pair_fn = \ ((env1_ids), ~(rec_ids)) -> (env_ids)
886 newSysLocalDs rec_ty `thenDs` \ rec_id ->
888 env1_id_set = fv_stmts `minusVarSet` rec_id_set
889 env1_ids = varSetElems env1_id_set
890 env1_ty = mkTupleType env1_ids
891 in_pair_ty = mkCorePairTy env1_ty rec_ty
892 core_body = mkBigCoreTup (map selectVar env_ids)
895 | v `elemVarSet` rec_id_set
896 = mkTupleSelector rec_ids v rec_id (Var rec_id)
899 matchEnvStack env1_ids [rec_id] core_body
900 `thenDs` \ squash_pair_fn ->
902 -- loop (arr squash_pair_fn >>> ss >>> arr mk_pair_fn)
905 env_ty = mkTupleType env_ids
906 core_loop = do_loop ids env1_ty later_ty rec_ty
907 (do_map_arrow ids in_pair_ty env_ty out_pair_ty
909 (do_compose ids env_ty out_ty out_pair_ty
911 (do_arr ids out_ty out_pair_ty mk_pair_fn)))
913 returnDs (core_loop, env1_id_set, env1_ids)
916 A sequence of statements (as in a rec) is desugared to an arrow between
921 :: DsCmdEnv -- arrow combinators
922 -> IdSet -- set of local vars available to this statement
923 -> [Id] -- output vars of these statements
924 -> [LStmt Id] -- statements to desugar
925 -> DsM (CoreExpr, -- desugared expression
926 IdSet, -- set of local vars that occur free
929 dsfixCmdStmts ids local_vars out_ids stmts
930 = fixDs (\ ~(_,_,env_ids) ->
931 dsCmdStmts ids local_vars env_ids out_ids stmts
932 `thenDs` \ (core_stmts, fv_stmts) ->
933 returnDs (core_stmts, fv_stmts, varSetElems fv_stmts))
936 :: DsCmdEnv -- arrow combinators
937 -> IdSet -- set of local vars available to this statement
938 -> [Id] -- list of vars in the input to these statements
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
944 dsCmdStmts ids local_vars env_ids out_ids [stmt]
945 = dsCmdLStmt ids local_vars env_ids out_ids stmt
947 dsCmdStmts ids local_vars env_ids out_ids (stmt:stmts)
949 bound_vars = mkVarSet (map unLoc (collectLStmtBinders stmt))
950 local_vars' = local_vars `unionVarSet` bound_vars
952 dsfixCmdStmts ids local_vars' out_ids stmts
953 `thenDs` \ (core_stmts, fv_stmts, env_ids') ->
954 dsCmdLStmt ids local_vars env_ids env_ids' stmt
955 `thenDs` \ (core_stmt, fv_stmt) ->
956 returnDs (do_compose ids
957 (mkTupleType env_ids)
958 (mkTupleType env_ids')
959 (mkTupleType out_ids)
966 Match a list of expressions against a list of patterns, left-to-right.
969 matchSimplys :: [CoreExpr] -- Scrutinees
970 -> HsMatchContext Name -- Match kind
971 -> [LPat Id] -- Patterns they should match
972 -> CoreExpr -- Return this if they all match
973 -> CoreExpr -- Return this if they don't
975 matchSimplys [] _ctxt [] result_expr _fail_expr = returnDs result_expr
976 matchSimplys (exp:exps) ctxt (pat:pats) result_expr fail_expr
977 = matchSimplys exps ctxt pats result_expr fail_expr
978 `thenDs` \ match_code ->
979 matchSimply exp ctxt pat match_code fail_expr
982 List of leaf expressions, with set of variables bound in each
985 leavesMatch :: LMatch Id -> [(LHsExpr Id, IdSet)]
986 leavesMatch (L _ (Match pats _ (GRHSs grhss binds _ty)))
988 defined_vars = mkVarSet (collectPatsBinders pats)
990 mkVarSet (map unLoc (collectGroupBinders binds))
993 mkVarSet (map unLoc (collectStmtsBinders stmts))
994 `unionVarSet` defined_vars)
995 | L _ (GRHS stmts) <- grhss,
996 let L _ (ResultStmt expr) = last stmts]
999 Replace the leaf commands in a match
1003 :: Type -- new result type
1004 -> [LHsExpr Id] -- replacement leaf expressions of that type
1005 -> LMatch Id -- the matches of a case command
1006 -> ([LHsExpr Id],-- remaining leaf expressions
1007 LMatch Id) -- updated match
1008 replaceLeavesMatch res_ty leaves (L loc (Match pat mt (GRHSs grhss binds _ty)))
1010 (leaves', grhss') = mapAccumL replaceLeavesGRHS leaves grhss
1012 (leaves', L loc (Match pat mt (GRHSs grhss' binds res_ty)))
1015 :: [LHsExpr Id] -- replacement leaf expressions of that type
1016 -> LGRHS Id -- rhss of a case command
1017 -> ([LHsExpr Id],-- remaining leaf expressions
1018 LGRHS Id) -- updated GRHS
1019 replaceLeavesGRHS (leaf:leaves) (L loc (GRHS stmts))
1020 = (leaves, L loc (GRHS (init stmts ++ [L (getLoc leaf) (ResultStmt leaf)])))
1023 Balanced fold of a non-empty list.
1026 foldb :: (a -> a -> a) -> [a] -> a
1027 foldb _ [] = error "foldb of empty list"
1029 foldb f xs = foldb f (fold_pairs xs)
1032 fold_pairs [x] = [x]
1033 fold_pairs (x1:x2:xs) = f x1 x2:fold_pairs xs