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 )
52 data DsCmdEnv = DsCmdEnv {
53 meth_binds :: [CoreBind],
54 arr_id, compose_id, first_id, app_id, choice_id, loop_id :: CoreExpr
57 mkCmdEnv :: SyntaxTable Id -> DsM DsCmdEnv
59 (meth_binds, ds_meths) <- dsSyntaxTable ids
61 meth_binds = meth_binds,
62 arr_id = Var (lookupEvidence ds_meths arrAName),
63 compose_id = Var (lookupEvidence ds_meths composeAName),
64 first_id = Var (lookupEvidence ds_meths firstAName),
65 app_id = Var (lookupEvidence ds_meths appAName),
66 choice_id = Var (lookupEvidence ds_meths choiceAName),
67 loop_id = Var (lookupEvidence ds_meths loopAName)
70 bindCmdEnv :: DsCmdEnv -> CoreExpr -> CoreExpr
71 bindCmdEnv ids body = foldr Let body (meth_binds ids)
73 -- arr :: forall b c. (b -> c) -> a b c
74 do_arr :: DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
75 do_arr ids b_ty c_ty f = mkApps (arr_id ids) [Type b_ty, Type c_ty, f]
77 -- (>>>) :: forall b c d. a b c -> a c d -> a b d
78 do_compose :: DsCmdEnv -> Type -> Type -> Type ->
79 CoreExpr -> CoreExpr -> CoreExpr
80 do_compose ids b_ty c_ty d_ty f g
81 = mkApps (compose_id ids) [Type b_ty, Type c_ty, Type d_ty, f, g]
83 -- first :: forall b c d. a b c -> a (b,d) (c,d)
84 do_first :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
85 do_first ids b_ty c_ty d_ty f
86 = mkApps (first_id ids) [Type b_ty, Type c_ty, Type d_ty, f]
88 -- app :: forall b c. a (a b c, b) c
89 do_app :: DsCmdEnv -> Type -> Type -> CoreExpr
90 do_app ids b_ty c_ty = mkApps (app_id ids) [Type b_ty, Type c_ty]
92 -- (|||) :: forall b d c. a b d -> a c d -> a (Either b c) d
93 -- note the swapping of d and c
94 do_choice :: DsCmdEnv -> Type -> Type -> Type ->
95 CoreExpr -> CoreExpr -> CoreExpr
96 do_choice ids b_ty c_ty d_ty f g
97 = mkApps (choice_id ids) [Type b_ty, Type d_ty, Type c_ty, f, g]
99 -- loop :: forall b d c. a (b,d) (c,d) -> a b c
100 -- note the swapping of d and c
101 do_loop :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
102 do_loop ids b_ty c_ty d_ty f
103 = mkApps (loop_id ids) [Type b_ty, Type d_ty, Type c_ty, f]
105 -- map_arrow (f :: b -> c) (g :: a c d) = arr f >>> g :: a b d
106 do_map_arrow :: DsCmdEnv -> Type -> Type -> Type ->
107 CoreExpr -> CoreExpr -> CoreExpr
108 do_map_arrow ids b_ty c_ty d_ty f c
109 = do_compose ids b_ty c_ty d_ty (do_arr ids b_ty c_ty f) c
111 mkFailExpr :: HsMatchContext Id -> Type -> DsM CoreExpr
113 = mkErrorAppDs pAT_ERROR_ID ty (matchContextErrString ctxt)
115 -- construct CoreExpr for \ (a :: a_ty, b :: b_ty) -> b
116 mkSndExpr :: Type -> Type -> DsM CoreExpr
117 mkSndExpr a_ty b_ty = do
118 a_var <- newSysLocalDs a_ty
119 b_var <- newSysLocalDs b_ty
120 pair_var <- newSysLocalDs (mkCorePairTy a_ty b_ty)
122 (coreCasePair pair_var a_var b_var (Var b_var)))
125 Build case analysis of a tuple. This cannot be done in the DsM monad,
126 because the list of variables is typically not yet defined.
129 -- coreCaseTuple [u1..] v [x1..xn] body
130 -- = case v of v { (x1, .., xn) -> body }
131 -- But the matching may be nested if the tuple is very big
133 coreCaseTuple :: UniqSupply -> Id -> [Id] -> CoreExpr -> CoreExpr
134 coreCaseTuple uniqs scrut_var vars body
135 = mkTupleCase uniqs vars body scrut_var (Var scrut_var)
137 coreCasePair :: Id -> Id -> Id -> CoreExpr -> CoreExpr
138 coreCasePair scrut_var var1 var2 body
139 = Case (Var scrut_var) scrut_var (exprType body)
140 [(DataAlt (tupleCon Boxed 2), [var1, var2], body)]
144 mkCorePairTy :: Type -> Type -> Type
145 mkCorePairTy t1 t2 = mkCoreTupTy [t1, t2]
147 mkCorePairExpr :: CoreExpr -> CoreExpr -> CoreExpr
148 mkCorePairExpr e1 e2 = mkCoreTup [e1, e2]
151 The input is divided into a local environment, which is a flat tuple
152 (unless it's too big), and a stack, each element of which is paired
153 with the stack in turn. In general, the input has the form
155 (...((x1,...,xn),s1),...sk)
157 where xi are the environment values, and si the ones on the stack,
158 with s1 being the "top", the first one to be matched with a lambda.
161 envStackType :: [Id] -> [Type] -> Type
162 envStackType ids stack_tys = foldl mkCorePairTy (mkBigCoreVarTupTy ids) stack_tys
164 ----------------------------------------------
167 -- (...((x1,...,xn),s1),...sk)
169 buildEnvStack :: [Id] -> [Id] -> CoreExpr
170 buildEnvStack env_ids stack_ids
171 = foldl mkCorePairExpr (mkBigCoreVarTup env_ids) (map Var stack_ids)
173 ----------------------------------------------
176 -- \ (...((x1,...,xn),s1),...sk) -> e
179 -- case zk of (zk-1,sk) ->
181 -- case z1 of (z0,s1) ->
182 -- case z0 of (x1,...,xn) ->
185 matchEnvStack :: [Id] -- x1..xn
189 matchEnvStack env_ids stack_ids body = do
190 uniqs <- newUniqueSupply
191 tup_var <- newSysLocalDs (mkBigCoreVarTupTy env_ids)
192 matchVarStack tup_var stack_ids
193 (coreCaseTuple uniqs tup_var env_ids body)
196 ----------------------------------------------
199 -- \ (...(z0,s1),...sk) -> e
202 -- case zk of (zk-1,sk) ->
204 -- case z1 of (z0,s1) ->
207 matchVarStack :: Id -- z0
211 matchVarStack env_id [] body
212 = return (Lam env_id body)
213 matchVarStack env_id (stack_id:stack_ids) body = do
214 pair_id <- newSysLocalDs (mkCorePairTy (idType env_id) (idType stack_id))
215 matchVarStack pair_id stack_ids
216 (coreCasePair pair_id env_id stack_id body)
220 mkHsTupleExpr :: [HsExpr Id] -> HsExpr Id
221 mkHsTupleExpr [e] = e
222 mkHsTupleExpr es = ExplicitTuple (map noLoc es) Boxed
224 mkHsPairExpr :: HsExpr Id -> HsExpr Id -> HsExpr Id
225 mkHsPairExpr e1 e2 = mkHsTupleExpr [e1, e2]
227 mkHsEnvStackExpr :: [Id] -> [Id] -> HsExpr Id
228 mkHsEnvStackExpr env_ids stack_ids
229 = foldl mkHsPairExpr (mkHsTupleExpr (map HsVar env_ids)) (map HsVar stack_ids)
232 Translation of arrow abstraction
236 -- A | xs |- c :: [] t' ---> c'
237 -- --------------------------
238 -- A |- proc p -> c :: a t t' ---> arr (\ p -> (xs)) >>> c'
240 -- where (xs) is the tuple of variables bound by p
246 dsProcExpr pat (L _ (HsCmdTop cmd [] cmd_ty ids)) = do
247 meth_ids <- mkCmdEnv ids
248 let locals = mkVarSet (collectPatBinders pat)
249 (core_cmd, _free_vars, env_ids) <- dsfixCmd meth_ids locals [] cmd_ty cmd
250 let env_ty = mkBigCoreVarTupTy env_ids
251 fail_expr <- mkFailExpr ProcExpr env_ty
252 var <- selectSimpleMatchVarL pat
253 match_code <- matchSimply (Var var) ProcExpr pat (mkBigCoreVarTup env_ids) fail_expr
254 let pat_ty = hsLPatType pat
255 proc_code = do_map_arrow meth_ids pat_ty env_ty cmd_ty
258 return (bindCmdEnv meth_ids proc_code)
259 dsProcExpr _ c = pprPanic "dsProcExpr" (ppr c)
262 Translation of command judgements of the form
264 A | xs |- c :: [ts] t
267 dsLCmd :: DsCmdEnv -> IdSet -> [Id] -> [Type] -> Type -> LHsCmd Id
268 -> DsM (CoreExpr, IdSet)
269 dsLCmd ids local_vars env_ids stack res_ty cmd
270 = dsCmd ids local_vars env_ids stack res_ty (unLoc cmd)
272 dsCmd :: DsCmdEnv -- arrow combinators
273 -> IdSet -- set of local vars available to this command
274 -> [Id] -- list of vars in the input to this command
275 -- This is typically fed back,
276 -- so don't pull on it too early
277 -> [Type] -- type of the stack
278 -> Type -- return type of the command
279 -> HsCmd Id -- command to desugar
280 -> DsM (CoreExpr, -- desugared expression
281 IdSet) -- set of local vars that occur free
283 -- A |- f :: a (t*ts) t'
285 -- -----------------------------
286 -- A | xs |- f -< arg :: [ts] t'
288 -- ---> arr (\ ((xs)*ts) -> (arg*ts)) >>> f
290 dsCmd ids local_vars env_ids stack res_ty
291 (HsArrApp arrow arg arrow_ty HsFirstOrderApp _)= do
293 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
294 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
295 core_arrow <- dsLExpr arrow
296 core_arg <- dsLExpr arg
297 stack_ids <- mapM newSysLocalDs stack
298 core_make_arg <- matchEnvStack env_ids stack_ids
299 (foldl mkCorePairExpr core_arg (map Var stack_ids))
300 return (do_map_arrow ids
301 (envStackType env_ids stack)
306 exprFreeVars core_arg `intersectVarSet` local_vars)
308 -- A, xs |- f :: a (t*ts) t'
310 -- ------------------------------
311 -- A | xs |- f -<< arg :: [ts] t'
313 -- ---> arr (\ ((xs)*ts) -> (f,(arg*ts))) >>> app
315 dsCmd ids local_vars env_ids stack res_ty
316 (HsArrApp arrow arg arrow_ty HsHigherOrderApp _) = do
318 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
319 (_a_ty, arg_ty) = tcSplitAppTy a_arg_ty
321 core_arrow <- dsLExpr arrow
322 core_arg <- dsLExpr arg
323 stack_ids <- mapM newSysLocalDs stack
324 core_make_pair <- matchEnvStack env_ids stack_ids
325 (mkCorePairExpr core_arrow
326 (foldl mkCorePairExpr core_arg (map Var stack_ids)))
328 return (do_map_arrow ids
329 (envStackType env_ids stack)
330 (mkCorePairTy arrow_ty arg_ty)
333 (do_app ids arg_ty res_ty),
334 (exprFreeVars core_arrow `unionVarSet` exprFreeVars core_arg)
335 `intersectVarSet` local_vars)
337 -- A | ys |- c :: [t:ts] t'
339 -- ------------------------
340 -- A | xs |- c e :: [ts] t'
342 -- ---> arr (\ ((xs)*ts) -> let z = e in (((ys),z)*ts)) >>> c
344 dsCmd ids local_vars env_ids stack res_ty (HsApp cmd arg) = do
345 core_arg <- dsLExpr arg
347 arg_ty = exprType core_arg
348 stack' = arg_ty:stack
349 (core_cmd, free_vars, env_ids')
350 <- dsfixCmd ids local_vars stack' res_ty cmd
351 stack_ids <- mapM newSysLocalDs stack
352 arg_id <- newSysLocalDs arg_ty
353 -- push the argument expression onto the stack
355 core_body = bindNonRec arg_id core_arg
356 (buildEnvStack env_ids' (arg_id:stack_ids))
357 -- match the environment and stack against the input
358 core_map <- matchEnvStack env_ids stack_ids core_body
359 return (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 (MatchGroup [L _ (Match pats _ (GRHSs [L _ (GRHS [] body)] _ ))] _)) = do
377 pat_vars = mkVarSet (collectPatsBinders pats)
378 local_vars' = local_vars `unionVarSet` pat_vars
379 stack' = drop (length pats) stack
380 (core_body, free_vars, env_ids') <- dsfixCmd ids local_vars' stack' res_ty body
381 stack_ids <- mapM newSysLocalDs stack
383 -- the expression is built from the inside out, so the actions
384 -- are presented in reverse order
387 (actual_ids, stack_ids') = splitAt (length pats) stack_ids
388 -- build a new environment, plus what's left of the stack
389 core_expr = buildEnvStack env_ids' stack_ids'
390 in_ty = envStackType env_ids stack
391 in_ty' = envStackType env_ids' stack'
393 fail_expr <- mkFailExpr LambdaExpr in_ty'
394 -- match the patterns against the top of the old stack
395 match_code <- matchSimplys (map Var actual_ids) LambdaExpr pats core_expr fail_expr
396 -- match the old environment and stack against the input
397 select_code <- matchEnvStack env_ids stack_ids match_code
398 return (do_map_arrow ids in_ty in_ty' res_ty select_code core_body,
399 free_vars `minusVarSet` pat_vars)
401 dsCmd ids local_vars env_ids stack res_ty (HsPar cmd)
402 = dsLCmd ids local_vars env_ids stack res_ty cmd
404 -- A, xs |- e :: Bool
405 -- A | xs1 |- c1 :: [ts] t
406 -- A | xs2 |- c2 :: [ts] t
407 -- ----------------------------------------
408 -- A | xs |- if e then c1 else c2 :: [ts] t
410 -- ---> arr (\ ((xs)*ts) ->
411 -- if e then Left ((xs1)*ts) else Right ((xs2)*ts)) >>>
414 dsCmd ids local_vars env_ids stack res_ty (HsIf cond then_cmd else_cmd) = do
415 core_cond <- dsLExpr cond
416 (core_then, fvs_then, then_ids) <- dsfixCmd ids local_vars stack res_ty then_cmd
417 (core_else, fvs_else, else_ids) <- dsfixCmd ids local_vars stack res_ty else_cmd
418 stack_ids <- mapM newSysLocalDs stack
419 either_con <- dsLookupTyCon eitherTyConName
420 left_con <- dsLookupDataCon leftDataConName
421 right_con <- dsLookupDataCon rightDataConName
423 left_expr ty1 ty2 e = mkConApp left_con [Type ty1, Type ty2, e]
424 right_expr ty1 ty2 e = mkConApp right_con [Type ty1, Type ty2, e]
426 in_ty = envStackType env_ids stack
427 then_ty = envStackType then_ids stack
428 else_ty = envStackType else_ids stack
429 sum_ty = mkTyConApp either_con [then_ty, else_ty]
430 fvs_cond = exprFreeVars core_cond `intersectVarSet` local_vars
432 core_if <- matchEnvStack env_ids stack_ids
433 (mkIfThenElse core_cond
434 (left_expr then_ty else_ty (buildEnvStack then_ids stack_ids))
435 (right_expr then_ty else_ty (buildEnvStack else_ids stack_ids)))
436 return (do_map_arrow ids in_ty sum_ty res_ty
438 (do_choice ids then_ty else_ty res_ty core_then core_else),
439 fvs_cond `unionVarSet` fvs_then `unionVarSet` fvs_else)
442 Case commands are treated in much the same way as if commands
443 (see above) except that there are more alternatives. For example
445 case e of { p1 -> c1; p2 -> c2; p3 -> c3 }
449 arr (\ ((xs)*ts) -> case e of
450 p1 -> (Left (Left (xs1)*ts))
451 p2 -> Left ((Right (xs2)*ts))
452 p3 -> Right ((xs3)*ts)) >>>
455 The idea is to extract the commands from the case, build a balanced tree
456 of choices, and replace the commands with expressions that build tagged
457 tuples, obtaining a case expression that can be desugared normally.
458 To build all this, we use quadruples decribing segments of the list of
459 case bodies, containing the following fields:
460 1. an IdSet containing the environment variables free in the case bodies
461 2. a list of expressions of the form (Left|Right)* ((xs)*ts), to be put
462 into the case replacing the commands
463 3. a sum type that is the common type of these expressions, and also the
464 input type of the arrow
465 4. a CoreExpr for an arrow built by combining the translated command
469 dsCmd ids local_vars env_ids stack res_ty (HsCase exp (MatchGroup matches match_ty)) = do
470 core_exp <- dsLExpr exp
471 stack_ids <- mapM newSysLocalDs stack
473 -- Extract and desugar the leaf commands in the case, building tuple
474 -- expressions that will (after tagging) replace these leaves
477 leaves = concatMap leavesMatch matches
478 make_branch (leaf, bound_vars) = do
479 (core_leaf, fvs, leaf_ids) <-
480 dsfixCmd ids (local_vars `unionVarSet` bound_vars) stack res_ty leaf
481 return (fvs `minusVarSet` bound_vars,
482 [noLoc $ mkHsEnvStackExpr leaf_ids stack_ids],
483 envStackType leaf_ids stack,
486 branches <- mapM make_branch leaves
487 either_con <- dsLookupTyCon eitherTyConName
488 left_con <- dsLookupDataCon leftDataConName
489 right_con <- dsLookupDataCon rightDataConName
491 left_id = HsVar (dataConWrapId left_con)
492 right_id = HsVar (dataConWrapId right_con)
493 left_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ HsWrap (mkWpTyApps [ty1, ty2]) left_id ) e
494 right_expr ty1 ty2 e = noLoc $ HsApp (noLoc $ HsWrap (mkWpTyApps [ty1, ty2]) right_id) e
496 -- Prefix each tuple with a distinct series of Left's and Right's,
497 -- in a balanced way, keeping track of the types.
499 merge_branches (fvs1, builds1, in_ty1, core_exp1)
500 (fvs2, builds2, in_ty2, core_exp2)
501 = (fvs1 `unionVarSet` fvs2,
502 map (left_expr in_ty1 in_ty2) builds1 ++
503 map (right_expr in_ty1 in_ty2) builds2,
504 mkTyConApp either_con [in_ty1, in_ty2],
505 do_choice ids in_ty1 in_ty2 res_ty core_exp1 core_exp2)
506 (fvs_alts, leaves', sum_ty, core_choices)
507 = foldb merge_branches branches
509 -- Replace the commands in the case with these tagged tuples,
510 -- yielding a HsExpr Id we can feed to dsExpr.
512 (_, matches') = mapAccumL (replaceLeavesMatch res_ty) leaves' matches
513 in_ty = envStackType env_ids stack
514 fvs_exp = exprFreeVars core_exp `intersectVarSet` local_vars
516 pat_ty = funArgTy match_ty
517 match_ty' = mkFunTy pat_ty sum_ty
518 -- Note that we replace the HsCase result type by sum_ty,
519 -- which is the type of matches'
521 core_body <- dsExpr (HsCase exp (MatchGroup matches' match_ty'))
522 core_matches <- matchEnvStack env_ids stack_ids core_body
523 return (do_map_arrow ids in_ty sum_ty res_ty core_matches core_choices,
524 fvs_exp `unionVarSet` fvs_alts)
526 -- A | ys |- c :: [ts] t
527 -- ----------------------------------
528 -- A | xs |- let binds in c :: [ts] t
530 -- ---> arr (\ ((xs)*ts) -> let binds in ((ys)*ts)) >>> c
532 dsCmd ids local_vars env_ids stack res_ty (HsLet binds body) = do
534 defined_vars = mkVarSet (map unLoc (collectLocalBinders binds))
535 local_vars' = local_vars `unionVarSet` defined_vars
537 (core_body, _free_vars, env_ids') <- dsfixCmd ids local_vars' stack res_ty body
538 stack_ids <- mapM newSysLocalDs stack
539 -- build a new environment, plus the stack, using the let bindings
540 core_binds <- dsLocalBinds binds (buildEnvStack env_ids' stack_ids)
541 -- match the old environment and stack against the input
542 core_map <- matchEnvStack env_ids stack_ids core_binds
543 return (do_map_arrow ids
544 (envStackType env_ids stack)
545 (envStackType env_ids' stack)
549 exprFreeVars core_binds `intersectVarSet` local_vars)
551 dsCmd ids local_vars env_ids [] res_ty (HsDo _ctxt stmts body _)
552 = dsCmdDo ids local_vars env_ids res_ty stmts body
554 -- A |- e :: forall e. a1 (e*ts1) t1 -> ... an (e*tsn) tn -> a (e*ts) t
555 -- A | xs |- ci :: [tsi] ti
556 -- -----------------------------------
557 -- A | xs |- (|e c1 ... cn|) :: [ts] t ---> e [t_xs] c1 ... cn
559 dsCmd _ids local_vars env_ids _stack _res_ty (HsArrForm op _ args) = do
560 let env_ty = mkBigCoreVarTupTy env_ids
561 core_op <- dsLExpr op
562 (core_args, fv_sets) <- mapAndUnzipM (dsTrimCmdArg local_vars env_ids) args
563 return (mkApps (App core_op (Type env_ty)) core_args,
564 unionVarSets fv_sets)
567 dsCmd ids local_vars env_ids stack res_ty (HsTick ix vars expr) = do
568 (expr1,id_set) <- dsLCmd ids local_vars env_ids stack res_ty expr
569 expr2 <- mkTickBox ix vars expr1
570 return (expr2,id_set)
572 dsCmd _ _ _ _ _ c = pprPanic "dsCmd" (ppr c)
574 -- A | ys |- c :: [ts] t (ys <= xs)
575 -- ---------------------
576 -- A | xs |- c :: [ts] t ---> arr_ts (\ (xs) -> (ys)) >>> c
579 :: IdSet -- set of local vars available to this command
580 -> [Id] -- list of vars in the input to this command
581 -> LHsCmdTop Id -- command argument to desugar
582 -> DsM (CoreExpr, -- desugared expression
583 IdSet) -- set of local vars that occur free
584 dsTrimCmdArg local_vars env_ids (L _ (HsCmdTop cmd stack cmd_ty ids)) = do
585 meth_ids <- mkCmdEnv ids
586 (core_cmd, free_vars, env_ids') <- dsfixCmd meth_ids local_vars stack cmd_ty cmd
587 stack_ids <- mapM newSysLocalDs stack
588 trim_code <- matchEnvStack env_ids stack_ids (buildEnvStack env_ids' stack_ids)
590 in_ty = envStackType env_ids stack
591 in_ty' = envStackType env_ids' stack
592 arg_code = if env_ids' == env_ids then core_cmd else
593 do_map_arrow meth_ids in_ty in_ty' cmd_ty trim_code core_cmd
594 return (bindCmdEnv meth_ids arg_code, free_vars)
596 -- Given A | xs |- c :: [ts] t, builds c with xs fed back.
597 -- Typically needs to be prefixed with arr (\p -> ((xs)*ts))
600 :: DsCmdEnv -- arrow combinators
601 -> IdSet -- set of local vars available to this command
602 -> [Type] -- type of the stack
603 -> Type -- return type of the command
604 -> LHsCmd Id -- command to desugar
605 -> DsM (CoreExpr, -- desugared expression
606 IdSet, -- set of local vars that occur free
607 [Id]) -- set as a list, fed back
608 dsfixCmd ids local_vars stack cmd_ty cmd
609 = fixDs (\ ~(_,_,env_ids') -> do
610 (core_cmd, free_vars) <- dsLCmd ids local_vars env_ids' stack cmd_ty cmd
611 return (core_cmd, free_vars, varSetElems free_vars))
615 Translation of command judgements of the form
617 A | xs |- do { ss } :: [] t
621 dsCmdDo :: DsCmdEnv -- arrow combinators
622 -> IdSet -- set of local vars available to this statement
623 -> [Id] -- list of vars in the input to this statement
624 -- This is typically fed back,
625 -- so don't pull on it too early
626 -> Type -- return type of the statement
627 -> [LStmt Id] -- statements to desugar
628 -> LHsExpr Id -- body
629 -> DsM (CoreExpr, -- desugared expression
630 IdSet) -- set of local vars that occur free
632 -- A | xs |- c :: [] t
633 -- --------------------------
634 -- A | xs |- do { c } :: [] t
636 dsCmdDo ids local_vars env_ids res_ty [] body
637 = dsLCmd ids local_vars env_ids [] res_ty body
639 dsCmdDo ids local_vars env_ids res_ty (stmt:stmts) body = do
641 bound_vars = mkVarSet (map unLoc (collectLStmtBinders stmt))
642 local_vars' = local_vars `unionVarSet` bound_vars
643 (core_stmts, _, env_ids') <- fixDs (\ ~(_,_,env_ids') -> do
644 (core_stmts, fv_stmts) <- dsCmdDo ids local_vars' env_ids' res_ty stmts body
645 return (core_stmts, fv_stmts, varSetElems fv_stmts))
646 (core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids env_ids' stmt
647 return (do_compose ids
648 (mkBigCoreVarTupTy env_ids)
649 (mkBigCoreVarTupTy env_ids')
656 A statement maps one local environment to another, and is represented
657 as an arrow from one tuple type to another. A statement sequence is
658 translated to a composition of such arrows.
660 dsCmdLStmt :: DsCmdEnv -> IdSet -> [Id] -> [Id] -> LStmt Id
661 -> DsM (CoreExpr, IdSet)
662 dsCmdLStmt ids local_vars env_ids out_ids cmd
663 = dsCmdStmt ids local_vars env_ids out_ids (unLoc cmd)
666 :: DsCmdEnv -- arrow combinators
667 -> IdSet -- set of local vars available to this statement
668 -> [Id] -- list of vars in the input to this statement
669 -- This is typically fed back,
670 -- so don't pull on it too early
671 -> [Id] -- list of vars in the output of this statement
672 -> Stmt Id -- statement to desugar
673 -> DsM (CoreExpr, -- desugared expression
674 IdSet) -- set of local vars that occur free
676 -- A | xs1 |- c :: [] t
677 -- A | xs' |- do { ss } :: [] t'
678 -- ------------------------------
679 -- A | xs |- do { c; ss } :: [] t'
681 -- ---> arr (\ (xs) -> ((xs1),(xs'))) >>> first c >>>
684 dsCmdStmt ids local_vars env_ids out_ids (ExprStmt cmd _ c_ty) = do
685 (core_cmd, fv_cmd, env_ids1) <- dsfixCmd ids local_vars [] c_ty cmd
686 core_mux <- matchEnvStack env_ids []
687 (mkCorePairExpr (mkBigCoreVarTup env_ids1) (mkBigCoreVarTup out_ids))
689 in_ty = mkBigCoreVarTupTy env_ids
690 in_ty1 = mkBigCoreVarTupTy env_ids1
691 out_ty = mkBigCoreVarTupTy out_ids
692 before_c_ty = mkCorePairTy in_ty1 out_ty
693 after_c_ty = mkCorePairTy c_ty out_ty
694 snd_fn <- mkSndExpr c_ty out_ty
695 return (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
696 do_compose ids before_c_ty after_c_ty out_ty
697 (do_first ids in_ty1 c_ty out_ty core_cmd) $
698 do_arr ids after_c_ty out_ty snd_fn,
699 extendVarSetList fv_cmd out_ids)
702 -- A | xs1 |- c :: [] t
703 -- A | xs' |- do { ss } :: [] t' xs2 = xs' - defs(p)
704 -- -----------------------------------
705 -- A | xs |- do { p <- c; ss } :: [] t'
707 -- ---> arr (\ (xs) -> ((xs1),(xs2))) >>> first c >>>
708 -- arr (\ (p, (xs2)) -> (xs')) >>> ss
710 -- It would be simpler and more consistent to do this using second,
711 -- but that's likely to be defined in terms of first.
713 dsCmdStmt ids local_vars env_ids out_ids (BindStmt pat cmd _ _) = do
714 (core_cmd, fv_cmd, env_ids1) <- dsfixCmd ids local_vars [] (hsLPatType pat) cmd
716 pat_ty = hsLPatType pat
717 pat_vars = mkVarSet (collectPatBinders pat)
718 env_ids2 = varSetElems (mkVarSet out_ids `minusVarSet` pat_vars)
719 env_ty2 = mkBigCoreVarTupTy env_ids2
721 -- multiplexing function
722 -- \ (xs) -> ((xs1),(xs2))
724 core_mux <- matchEnvStack env_ids []
725 (mkCorePairExpr (mkBigCoreVarTup env_ids1) (mkBigCoreVarTup env_ids2))
727 -- projection function
728 -- \ (p, (xs2)) -> (zs)
730 env_id <- newSysLocalDs env_ty2
731 uniqs <- newUniqueSupply
733 after_c_ty = mkCorePairTy pat_ty env_ty2
734 out_ty = mkBigCoreVarTupTy out_ids
735 body_expr = coreCaseTuple uniqs env_id env_ids2 (mkBigCoreVarTup out_ids)
737 fail_expr <- mkFailExpr (StmtCtxt DoExpr) out_ty
738 pat_id <- selectSimpleMatchVarL pat
739 match_code <- matchSimply (Var pat_id) (StmtCtxt DoExpr) pat body_expr fail_expr
740 pair_id <- newSysLocalDs after_c_ty
742 proj_expr = Lam pair_id (coreCasePair pair_id pat_id env_id match_code)
744 -- put it all together
746 in_ty = mkBigCoreVarTupTy env_ids
747 in_ty1 = mkBigCoreVarTupTy env_ids1
748 in_ty2 = mkBigCoreVarTupTy env_ids2
749 before_c_ty = mkCorePairTy in_ty1 in_ty2
750 return (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
751 do_compose ids before_c_ty after_c_ty out_ty
752 (do_first ids in_ty1 pat_ty in_ty2 core_cmd) $
753 do_arr ids after_c_ty out_ty proj_expr,
754 fv_cmd `unionVarSet` (mkVarSet out_ids `minusVarSet` pat_vars))
756 -- A | xs' |- do { ss } :: [] t
757 -- --------------------------------------
758 -- A | xs |- do { let binds; ss } :: [] t
760 -- ---> arr (\ (xs) -> let binds in (xs')) >>> ss
762 dsCmdStmt ids local_vars env_ids out_ids (LetStmt binds) = do
763 -- build a new environment using the let bindings
764 core_binds <- dsLocalBinds binds (mkBigCoreVarTup out_ids)
765 -- match the old environment against the input
766 core_map <- matchEnvStack env_ids [] core_binds
768 (mkBigCoreVarTupTy env_ids)
769 (mkBigCoreVarTupTy out_ids)
771 exprFreeVars core_binds `intersectVarSet` local_vars)
773 -- A | ys |- do { ss; returnA -< ((xs1), (ys2)) } :: [] ...
774 -- A | xs' |- do { ss' } :: [] t
775 -- ------------------------------------
776 -- A | xs |- do { rec ss; ss' } :: [] t
778 -- xs1 = xs' /\ defs(ss)
779 -- xs2 = xs' - defs(ss)
780 -- ys1 = ys - defs(ss)
781 -- ys2 = ys /\ defs(ss)
783 -- ---> arr (\(xs) -> ((ys1),(xs2))) >>>
784 -- first (loop (arr (\((ys1),~(ys2)) -> (ys)) >>> ss)) >>>
785 -- arr (\((xs1),(xs2)) -> (xs')) >>> ss'
787 dsCmdStmt ids local_vars env_ids out_ids (RecStmt stmts later_ids rec_ids rhss _binds) = do
788 let -- ToDo: ****** binds not desugared; ROSS PLEASE FIX ********
789 env2_id_set = mkVarSet out_ids `minusVarSet` mkVarSet later_ids
790 env2_ids = varSetElems env2_id_set
791 env2_ty = mkBigCoreVarTupTy env2_ids
793 -- post_loop_fn = \((later_ids),(env2_ids)) -> (out_ids)
795 uniqs <- newUniqueSupply
796 env2_id <- newSysLocalDs env2_ty
798 later_ty = mkBigCoreVarTupTy later_ids
799 post_pair_ty = mkCorePairTy later_ty env2_ty
800 post_loop_body = coreCaseTuple uniqs env2_id env2_ids (mkBigCoreVarTup out_ids)
802 post_loop_fn <- matchEnvStack later_ids [env2_id] post_loop_body
806 (core_loop, env1_id_set, env1_ids)
807 <- dsRecCmd ids local_vars stmts later_ids rec_ids rhss
809 -- pre_loop_fn = \(env_ids) -> ((env1_ids),(env2_ids))
812 env1_ty = mkBigCoreVarTupTy env1_ids
813 pre_pair_ty = mkCorePairTy env1_ty env2_ty
814 pre_loop_body = mkCorePairExpr (mkBigCoreVarTup env1_ids)
815 (mkBigCoreVarTup env2_ids)
817 pre_loop_fn <- matchEnvStack env_ids [] pre_loop_body
819 -- arr pre_loop_fn >>> first (loop (...)) >>> arr post_loop_fn
822 env_ty = mkBigCoreVarTupTy env_ids
823 out_ty = mkBigCoreVarTupTy out_ids
824 core_body = do_map_arrow ids env_ty pre_pair_ty out_ty
826 (do_compose ids pre_pair_ty post_pair_ty out_ty
827 (do_first ids env1_ty later_ty env2_ty
829 (do_arr ids post_pair_ty out_ty
832 return (core_body, env1_id_set `unionVarSet` env2_id_set)
834 dsCmdStmt _ _ _ _ s = pprPanic "dsCmdStmt" (ppr s)
836 -- loop (arr (\ ((env1_ids), ~(rec_ids)) -> (env_ids)) >>>
838 -- arr (\ (out_ids) -> ((later_ids),(rhss))) >>>
840 dsRecCmd :: DsCmdEnv -> VarSet -> [LStmt Id] -> [Var] -> [Var] -> [HsExpr Id]
841 -> DsM (CoreExpr, VarSet, [Var])
842 dsRecCmd ids local_vars stmts later_ids rec_ids rhss = do
844 rec_id_set = mkVarSet rec_ids
845 out_ids = varSetElems (mkVarSet later_ids `unionVarSet` rec_id_set)
846 out_ty = mkBigCoreVarTupTy out_ids
847 local_vars' = local_vars `unionVarSet` rec_id_set
849 -- mk_pair_fn = \ (out_ids) -> ((later_ids),(rhss))
851 core_rhss <- mapM dsExpr rhss
853 later_tuple = mkBigCoreVarTup later_ids
854 later_ty = mkBigCoreVarTupTy later_ids
855 rec_tuple = mkBigCoreTup core_rhss
856 rec_ty = mkBigCoreVarTupTy rec_ids
857 out_pair = mkCorePairExpr later_tuple rec_tuple
858 out_pair_ty = mkCorePairTy later_ty rec_ty
860 mk_pair_fn <- matchEnvStack out_ids [] out_pair
864 (core_stmts, fv_stmts, env_ids) <- dsfixCmdStmts ids local_vars' out_ids stmts
866 -- squash_pair_fn = \ ((env1_ids), ~(rec_ids)) -> (env_ids)
868 rec_id <- newSysLocalDs rec_ty
870 env1_id_set = fv_stmts `minusVarSet` rec_id_set
871 env1_ids = varSetElems env1_id_set
872 env1_ty = mkBigCoreVarTupTy env1_ids
873 in_pair_ty = mkCorePairTy env1_ty rec_ty
874 core_body = mkBigCoreTup (map selectVar env_ids)
877 | v `elemVarSet` rec_id_set
878 = mkTupleSelector rec_ids v rec_id (Var rec_id)
881 squash_pair_fn <- matchEnvStack env1_ids [rec_id] core_body
883 -- loop (arr squash_pair_fn >>> ss >>> arr mk_pair_fn)
886 env_ty = mkBigCoreVarTupTy env_ids
887 core_loop = do_loop ids env1_ty later_ty rec_ty
888 (do_map_arrow ids in_pair_ty env_ty out_pair_ty
890 (do_compose ids env_ty out_ty out_pair_ty
892 (do_arr ids out_ty out_pair_ty mk_pair_fn)))
894 return (core_loop, env1_id_set, env1_ids)
897 A sequence of statements (as in a rec) is desugared to an arrow between
902 :: DsCmdEnv -- arrow combinators
903 -> IdSet -- set of local vars available to this statement
904 -> [Id] -- output vars of these statements
905 -> [LStmt Id] -- statements to desugar
906 -> DsM (CoreExpr, -- desugared expression
907 IdSet, -- set of local vars that occur free
910 dsfixCmdStmts ids local_vars out_ids stmts
911 = fixDs (\ ~(_,_,env_ids) -> do
912 (core_stmts, fv_stmts) <- dsCmdStmts ids local_vars env_ids out_ids stmts
913 return (core_stmts, fv_stmts, varSetElems fv_stmts))
916 :: DsCmdEnv -- arrow combinators
917 -> IdSet -- set of local vars available to this statement
918 -> [Id] -- list of vars in the input to these statements
919 -> [Id] -- output vars of these statements
920 -> [LStmt Id] -- statements to desugar
921 -> DsM (CoreExpr, -- desugared expression
922 IdSet) -- set of local vars that occur free
924 dsCmdStmts ids local_vars env_ids out_ids [stmt]
925 = dsCmdLStmt ids local_vars env_ids out_ids stmt
927 dsCmdStmts ids local_vars env_ids out_ids (stmt:stmts) = do
929 bound_vars = mkVarSet (map unLoc (collectLStmtBinders stmt))
930 local_vars' = local_vars `unionVarSet` bound_vars
931 (core_stmts, _fv_stmts, env_ids') <- dsfixCmdStmts ids local_vars' out_ids stmts
932 (core_stmt, fv_stmt) <- dsCmdLStmt ids local_vars env_ids env_ids' stmt
933 return (do_compose ids
934 (mkBigCoreVarTupTy env_ids)
935 (mkBigCoreVarTupTy env_ids')
936 (mkBigCoreVarTupTy out_ids)
941 dsCmdStmts _ _ _ _ [] = panic "dsCmdStmts []"
945 Match a list of expressions against a list of patterns, left-to-right.
948 matchSimplys :: [CoreExpr] -- Scrutinees
949 -> HsMatchContext Name -- Match kind
950 -> [LPat Id] -- Patterns they should match
951 -> CoreExpr -- Return this if they all match
952 -> CoreExpr -- Return this if they don't
954 matchSimplys [] _ctxt [] result_expr _fail_expr = return result_expr
955 matchSimplys (exp:exps) ctxt (pat:pats) result_expr fail_expr = do
956 match_code <- matchSimplys exps ctxt pats result_expr fail_expr
957 matchSimply exp ctxt pat match_code fail_expr
958 matchSimplys _ _ _ _ _ = panic "matchSimplys"
961 List of leaf expressions, with set of variables bound in each
964 leavesMatch :: LMatch Id -> [(LHsExpr Id, IdSet)]
965 leavesMatch (L _ (Match pats _ (GRHSs grhss binds)))
967 defined_vars = mkVarSet (collectPatsBinders pats)
969 mkVarSet (map unLoc (collectLocalBinders binds))
972 mkVarSet (map unLoc (collectLStmtsBinders stmts))
973 `unionVarSet` defined_vars)
974 | L _ (GRHS stmts expr) <- grhss]
977 Replace the leaf commands in a match
981 :: Type -- new result type
982 -> [LHsExpr Id] -- replacement leaf expressions of that type
983 -> LMatch Id -- the matches of a case command
984 -> ([LHsExpr Id],-- remaining leaf expressions
985 LMatch Id) -- updated match
986 replaceLeavesMatch _res_ty leaves (L loc (Match pat mt (GRHSs grhss binds)))
988 (leaves', grhss') = mapAccumL replaceLeavesGRHS leaves grhss
990 (leaves', L loc (Match pat mt (GRHSs grhss' binds)))
993 :: [LHsExpr Id] -- replacement leaf expressions of that type
994 -> LGRHS Id -- rhss of a case command
995 -> ([LHsExpr Id],-- remaining leaf expressions
996 LGRHS Id) -- updated GRHS
997 replaceLeavesGRHS (leaf:leaves) (L loc (GRHS stmts _))
998 = (leaves, L loc (GRHS stmts leaf))
999 replaceLeavesGRHS [] _ = panic "replaceLeavesGRHS []"
1002 Balanced fold of a non-empty list.
1005 foldb :: (a -> a -> a) -> [a] -> a
1006 foldb _ [] = error "foldb of empty list"
1008 foldb f xs = foldb f (fold_pairs xs)
1011 fold_pairs [x] = [x]
1012 fold_pairs (x1:x2:xs) = f x1 x2:fold_pairs xs
1015 The following functions to collect value variables from patterns are
1016 copied from HsUtils, with one change: we also collect the dictionary
1017 bindings (pat_binds) from ConPatOut. We need them for cases like
1019 h :: Arrow a => Int -> a (Int,Int) Int
1020 h x = proc (y,z) -> case compare x y of
1021 GT -> returnA -< z+x
1023 The type checker turns the case into
1026 GT { p77 = plusInt } -> returnA -< p77 z x
1028 Here p77 is a local binding for the (+) operation.
1030 See comments in HsUtils for why the other version does not include
1034 collectPatBinders :: OutputableBndr a => LPat a -> [a]
1035 collectPatBinders pat = map unLoc (collectLocatedPatBinders pat)
1037 collectLocatedPatBinders :: OutputableBndr a => LPat a -> [Located a]
1038 collectLocatedPatBinders pat = collectl pat []
1040 collectPatsBinders :: OutputableBndr a => [LPat a] -> [a]
1041 collectPatsBinders pats = map unLoc (collectLocatedPatsBinders pats)
1043 collectLocatedPatsBinders :: OutputableBndr a => [LPat a] -> [Located a]
1044 collectLocatedPatsBinders pats = foldr collectl [] pats
1046 ---------------------
1047 collectl :: OutputableBndr a => LPat a -> [Located a] -> [Located a]
1048 collectl (L l pat) bndrs
1051 go (VarPat var) = L l var : bndrs
1052 go (VarPatOut var bs) = L l var : collectHsBindLocatedBinders bs
1054 go (WildPat _) = bndrs
1055 go (LazyPat pat) = collectl pat bndrs
1056 go (BangPat pat) = collectl pat bndrs
1057 go (AsPat a pat) = a : collectl pat bndrs
1058 go (ParPat pat) = collectl pat bndrs
1060 go (ListPat pats _) = foldr collectl bndrs pats
1061 go (PArrPat pats _) = foldr collectl bndrs pats
1062 go (TuplePat pats _ _) = foldr collectl bndrs pats
1064 go (ConPatIn _ ps) = foldr collectl bndrs (hsConPatArgs ps)
1065 go (ConPatOut {pat_args=ps, pat_binds=ds}) =
1066 collectHsBindLocatedBinders ds
1067 ++ foldr collectl bndrs (hsConPatArgs ps)
1068 go (LitPat _) = bndrs
1069 go (NPat _ _ _) = bndrs
1070 go (NPlusKPat n _ _ _) = n : bndrs
1072 go (SigPatIn pat _) = collectl pat bndrs
1073 go (SigPatOut pat _) = collectl pat bndrs
1074 go (TypePat _) = bndrs
1075 go (CoPat _ pat _) = collectl (noLoc pat) bndrs
1076 go p = pprPanic "collectl/go" (ppr p)