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, selectMatchVar,
14 mkTupleExpr, mkTupleSelector,
15 dsReboundNames, lookupReboundName )
18 import HsSyn ( HsExpr(..), Pat(..),
19 Stmt(..), HsMatchContext(..), HsStmtContext(..),
20 Match(..), GRHSs(..), GRHS(..),
21 HsCmdTop(..), HsArrAppType(..),
24 collectStmtBinders, collectStmtsBinders,
27 import TcHsSyn ( TypecheckedHsCmd, TypecheckedHsCmdTop,
28 TypecheckedHsExpr, TypecheckedHsBinds,
30 TypecheckedMatch, TypecheckedGRHSs, TypecheckedGRHS,
31 TypecheckedStmt, hsPatType,
32 TypecheckedMatchContext )
34 -- NB: The desugarer, which straddles the source and Core worlds, sometimes
35 -- needs to see source types (newtypes etc), and sometimes not
36 -- So WATCH OUT; check each use of split*Ty functions.
37 -- Sigh. This is a pain.
39 import {-# SOURCE #-} DsExpr ( dsExpr, dsLet )
41 import TcType ( Type, tcSplitAppTy )
42 import Type ( mkTyConApp )
44 import CoreFVs ( exprFreeVars )
45 import CoreUtils ( exprType, mkIfThenElse, bindNonRec )
47 import Id ( Id, idType )
48 import PrelInfo ( pAT_ERROR_ID )
49 import DataCon ( DataCon, dataConWrapId )
50 import TysWiredIn ( tupleCon, mkTupleTy )
51 import BasicTypes ( Boxity(..) )
52 import PrelNames ( eitherTyConName, leftDataConName, rightDataConName,
53 arrAName, composeAName, firstAName,
54 appAName, choiceAName, loopAName )
55 import Util ( mapAccumL )
58 import HsPat ( collectPatBinders, collectPatsBinders )
59 import VarSet ( IdSet, emptyVarSet, mkVarSet, varSetElems,
60 intersectVarSet, minusVarSet,
61 unionVarSet, unionVarSets, elemVarSet )
62 import SrcLoc ( SrcLoc )
66 data DsCmdEnv = DsCmdEnv {
67 meth_binds :: [CoreBind],
68 arr_id, compose_id, first_id, app_id, choice_id, loop_id :: CoreExpr
71 mkCmdEnv :: ReboundNames Id -> DsM DsCmdEnv
73 = dsReboundNames ids `thenDs` \ (meth_binds, ds_meths) ->
75 meth_binds = meth_binds,
76 arr_id = lookupReboundName ds_meths arrAName,
77 compose_id = lookupReboundName ds_meths composeAName,
78 first_id = lookupReboundName ds_meths firstAName,
79 app_id = lookupReboundName ds_meths appAName,
80 choice_id = lookupReboundName ds_meths choiceAName,
81 loop_id = lookupReboundName ds_meths loopAName
84 bindCmdEnv :: DsCmdEnv -> CoreExpr -> CoreExpr
85 bindCmdEnv ids body = foldr Let body (meth_binds ids)
87 -- arr :: forall b c. (b -> c) -> a b c
88 do_arr :: DsCmdEnv -> Type -> Type -> CoreExpr -> CoreExpr
89 do_arr ids b_ty c_ty f = mkApps (arr_id ids) [Type b_ty, Type c_ty, f]
91 -- (>>>) :: forall b c d. a b c -> a c d -> a b d
92 do_compose :: DsCmdEnv -> Type -> Type -> Type ->
93 CoreExpr -> CoreExpr -> CoreExpr
94 do_compose ids b_ty c_ty d_ty f g
95 = mkApps (compose_id ids) [Type b_ty, Type c_ty, Type d_ty, f, g]
97 -- first :: forall b c d. a b c -> a (b,d) (c,d)
98 do_first :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
99 do_first ids b_ty c_ty d_ty f
100 = mkApps (first_id ids) [Type b_ty, Type c_ty, Type d_ty, f]
102 -- app :: forall b c. a (a b c, b) c
103 do_app :: DsCmdEnv -> Type -> Type -> CoreExpr
104 do_app ids b_ty c_ty = mkApps (app_id ids) [Type b_ty, Type c_ty]
106 -- (|||) :: forall b d c. a b d -> a c d -> a (Either b c) d
107 -- note the swapping of d and c
108 do_choice :: DsCmdEnv -> Type -> Type -> Type ->
109 CoreExpr -> CoreExpr -> CoreExpr
110 do_choice ids b_ty c_ty d_ty f g
111 = mkApps (choice_id ids) [Type b_ty, Type d_ty, Type c_ty, f, g]
113 -- loop :: forall b d c. a (b,d) (c,d) -> a b c
114 -- note the swapping of d and c
115 do_loop :: DsCmdEnv -> Type -> Type -> Type -> CoreExpr -> CoreExpr
116 do_loop ids b_ty c_ty d_ty f
117 = mkApps (loop_id ids) [Type b_ty, Type d_ty, Type c_ty, f]
119 -- map_arrow (f :: b -> c) (g :: a c d) = arr f >>> g :: a b d
120 do_map_arrow :: DsCmdEnv -> Type -> Type -> Type ->
121 CoreExpr -> CoreExpr -> CoreExpr
122 do_map_arrow ids b_ty c_ty d_ty f c
123 = do_compose ids b_ty c_ty d_ty (do_arr ids b_ty c_ty f) c
125 mkFailExpr :: TypecheckedMatchContext -> Type -> DsM CoreExpr
127 = mkErrorAppDs pAT_ERROR_ID ty (matchContextErrString ctxt)
129 -- construct CoreExpr for \ (a :: a_ty, b :: b_ty) -> b
130 mkSndExpr :: Type -> Type -> DsM CoreExpr
132 = newSysLocalDs a_ty `thenDs` \a_var ->
133 newSysLocalDs b_ty `thenDs` \b_var ->
134 newSysLocalDs (mkCorePairTy a_ty b_ty) `thenDs` \pair_var ->
135 returnDs (coreCaseSmallTuple pair_var [a_var, b_var] (Var b_var))
138 Build case analysis of a tuple. This cannot be done in the DsM monad,
139 because the list of variables is typically not yet defined.
142 -- coreCaseTuple [u1..] v [x1..xn] body
143 -- = case v of v { (x1, .., xn) -> body }
144 -- But the matching may be nested if the tuple is very big
146 coreCaseTuple :: UniqSupply -> Id -> [Id] -> CoreExpr -> CoreExpr
147 coreCaseTuple uniqs = coreCaseSmallTuple -- TODO: do this right
149 -- same, but with a tuple small enough not to need nesting
151 coreCaseSmallTuple :: Id -> [Id] -> CoreExpr -> CoreExpr
152 coreCaseSmallTuple scrut_var [var] body
153 = bindNonRec var (Var scrut_var) body
154 coreCaseSmallTuple scrut_var vars body
155 = Case (Var scrut_var) scrut_var
156 [(DataAlt (tupleCon Boxed (length vars)), vars, body)]
160 -- Not right: doesn't handle nested tuples
161 tupleType :: [Id] -> Type
162 tupleType vars = mkCoreTupTy (map idType vars)
164 mkCorePairTy :: Type -> Type -> Type
165 mkCorePairTy t1 t2 = mkCoreTupTy [t1, t2]
167 mkCorePairExpr :: CoreExpr -> CoreExpr -> CoreExpr
168 mkCorePairExpr e1 e2 = mkCoreTup [e1, e2]
171 The input is divided into a local environment, which is a flat tuple
172 (unless it's too big), and a stack, each element of which is paired
173 with the stack in turn. In general, the input has the form
175 (...((x1,...,xn),s1),...sk)
177 where xi are the environment values, and si the ones on the stack,
178 with s1 being the "top", the first one to be matched with a lambda.
181 envStackType :: [Id] -> [Type] -> Type
182 envStackType ids stack_tys = foldl mkCorePairTy (tupleType ids) stack_tys
184 ----------------------------------------------
187 -- (...((x1,...,xn),s1),...sn)
189 buildEnvStack :: [Id] -> [Id] -> CoreExpr
190 buildEnvStack env_ids stack_ids
191 = envStackExpr (mkTupleExpr env_ids) (map Var stack_ids)
193 envStackExpr :: CoreExpr -> [CoreExpr] -> CoreExpr
194 envStackExpr core_ids core_exprs = foldl mkCorePairExpr core_ids core_exprs
196 ----------------------------------------------
199 -- \ (...((x1,...,xm),s1),...sn) -> e
202 -- case zn of (zn-1,sn) ->
204 -- case z1 of (z0,s1) ->
205 -- case z0 of (x1,...,xm) ->
208 matchEnvStack :: [Id] -- x1..xm
212 matchEnvStack env_ids stack_ids body
213 = getUniqSupplyDs `thenDs` \ uniqs ->
214 newSysLocalDs (tupleType env_ids) `thenDs` \ tup_var ->
215 matchVarStack tup_var stack_ids
216 (coreCaseTuple uniqs tup_var env_ids body)
219 ----------------------------------------------
222 -- \ (...(z0,s1),...sn) -> e
225 -- case zn of (zn-1,sn) ->
227 -- case z1 of (z0,s1) ->
230 matchVarStack :: Id -- z0
234 matchVarStack env_id [] body
235 = returnDs (Lam env_id body)
236 matchVarStack env_id (stack_id:stack_ids) body
238 pair_ids = [env_id, stack_id]
240 newSysLocalDs (tupleType pair_ids) `thenDs` \ pair_id ->
241 matchVarStack pair_id stack_ids
242 (coreCaseSmallTuple pair_id pair_ids body)
246 mkHsTupleExpr :: [TypecheckedHsExpr] -> TypecheckedHsExpr
247 mkHsTupleExpr [e] = e
248 mkHsTupleExpr es = ExplicitTuple es Unboxed
250 mkHsPairExpr :: TypecheckedHsExpr -> TypecheckedHsExpr -> TypecheckedHsExpr
251 mkHsPairExpr e1 e2 = mkHsTupleExpr [e1, e2]
253 mkHsEnvStackExpr :: [Id] -> [Id] -> TypecheckedHsExpr
254 mkHsEnvStackExpr env_ids stack_ids
255 = foldl mkHsPairExpr (mkHsTupleExpr (map HsVar env_ids)) (map HsVar stack_ids)
258 Translation of arrow abstraction
262 -- A | xs |- c :: [] t' ---> c'
263 -- --------------------------
264 -- A |- proc p -> c :: a t t' ---> arr (\ p -> (xs)) >>> c'
266 -- where (xs) is the tuple of variables bound by p
270 -> TypecheckedHsCmdTop
273 dsProcExpr pat (HsCmdTop cmd [] cmd_ty ids) locn
275 mkCmdEnv ids `thenDs` \ meth_ids ->
277 locals = mkVarSet (collectPatBinders pat)
279 dsfixCmd meth_ids locals [] cmd_ty cmd
280 `thenDs` \ (core_cmd, free_vars, env_ids) ->
282 env_ty = tupleType env_ids
284 mkFailExpr ProcExpr env_ty `thenDs` \ fail_expr ->
285 selectMatchVar pat `thenDs` \ var ->
286 matchSimply (Var var) ProcExpr pat (mkTupleExpr env_ids) fail_expr
287 `thenDs` \ match_code ->
289 pat_ty = hsPatType pat
290 proc_code = do_map_arrow meth_ids pat_ty env_ty cmd_ty
294 returnDs (bindCmdEnv meth_ids proc_code)
298 Translation of command judgements of the form
300 A | xs |- c :: [ts] t
304 dsCmd :: DsCmdEnv -- arrow combinators
305 -> IdSet -- set of local vars available to this command
306 -> [Id] -- list of vars in the input to this command
307 -- This is typically fed back,
308 -- so don't pull on it too early
309 -> [Type] -- type of the stack
310 -> Type -- return type of the command
311 -> TypecheckedHsCmd -- command to desugar
312 -> DsM (CoreExpr, -- desugared expression
313 IdSet) -- set of local vars that occur free
317 -- ---------------------------
318 -- A | xs |- f -< arg :: [] t' ---> arr (\ (xs) -> arg) >>> f
320 dsCmd ids local_vars env_ids [] res_ty
321 (HsArrApp arrow arg arrow_ty HsFirstOrderApp _ _)
323 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
324 (a_ty, arg_ty) = tcSplitAppTy a_arg_ty
325 env_ty = tupleType env_ids
327 dsExpr arrow `thenDs` \ core_arrow ->
328 dsExpr arg `thenDs` \ core_arg ->
329 matchEnvStack env_ids [] core_arg `thenDs` \ core_make_arg ->
330 returnDs (do_map_arrow ids env_ty arg_ty res_ty
333 exprFreeVars core_arg `intersectVarSet` local_vars)
335 -- A, xs |- f :: a t t'
337 -- ---------------------------
338 -- A | xs |- f -<< arg :: [] t' ---> arr (\ (xs) -> (f,arg)) >>> app
340 dsCmd ids local_vars env_ids [] res_ty
341 (HsArrApp arrow arg arrow_ty HsHigherOrderApp _ _)
343 (a_arg_ty, _res_ty') = tcSplitAppTy arrow_ty
344 (a_ty, arg_ty) = tcSplitAppTy a_arg_ty
345 env_ty = tupleType env_ids
347 dsExpr arrow `thenDs` \ core_arrow ->
348 dsExpr arg `thenDs` \ core_arg ->
349 matchEnvStack env_ids [] (mkCoreTup [core_arrow, core_arg])
350 `thenDs` \ core_make_pair ->
351 returnDs (do_map_arrow ids env_ty (mkCorePairTy arrow_ty arg_ty) res_ty
353 (do_app ids arg_ty res_ty),
354 (exprFreeVars core_arrow `unionVarSet` exprFreeVars core_arg)
355 `intersectVarSet` local_vars)
357 -- A | ys |- c :: [ts] t'
358 -- -----------------------------------------------
359 -- A | xs |- \ p1 ... pk -> c :: [t1:...:tk:ts] t'
361 -- ---> arr (\ ((((xs), p1), ... pk)*ts) -> ((ys)*ts)) >>> c
363 dsCmd ids local_vars env_ids stack res_ty
364 (HsLam (Match pats _ (GRHSs [GRHS [ResultStmt body _] loc] _ _cmd_ty)))
366 pat_vars = mkVarSet (collectPatsBinders pats)
367 local_vars' = local_vars `unionVarSet` pat_vars
368 stack' = drop (length pats) stack
370 dsfixCmd ids local_vars' stack' res_ty body
371 `thenDs` \ (core_body, free_vars, env_ids') ->
372 mapDs newSysLocalDs stack `thenDs` \ stack_ids ->
374 -- the expression is built from the inside out, so the actions
375 -- are presented in reverse order
378 (actual_ids, stack_ids') = splitAt (length pats) stack_ids
379 -- build a new environment, plus what's left of the stack
380 core_expr = buildEnvStack env_ids' stack_ids'
381 in_ty = envStackType env_ids stack
382 in_ty' = envStackType env_ids' stack'
384 mkFailExpr LambdaExpr in_ty' `thenDs` \ fail_expr ->
385 -- match the patterns against the top of the old stack
386 matchSimplys (map Var actual_ids) LambdaExpr pats core_expr fail_expr
387 `thenDs` \ match_code ->
388 -- match the old environment and stack against the input
389 matchEnvStack env_ids stack_ids match_code
390 `thenDs` \ select_code ->
391 returnDs (do_map_arrow ids in_ty in_ty' res_ty select_code core_body,
392 free_vars `minusVarSet` pat_vars)
394 dsCmd ids local_vars env_ids stack res_ty (HsPar cmd)
395 = dsCmd ids local_vars env_ids stack res_ty cmd
397 dsCmd ids local_vars env_ids stack res_ty (HsCase exp matches src_loc)
398 = dsExpr exp `thenDs` \ core_exp ->
399 mapDs newSysLocalDs stack `thenDs` \ stack_ids ->
401 -- Extract and desugar the leaf commands in the case, building tuple
402 -- expressions that will (after tagging) replace these leaves
405 leaves = concatMap leavesMatch matches
406 make_branch (leaf, bound_vars)
407 = dsfixCmd ids (local_vars `unionVarSet` bound_vars) stack res_ty leaf
408 `thenDs` \ (core_leaf, fvs, leaf_ids) ->
409 returnDs (fvs `minusVarSet` bound_vars,
410 [mkHsEnvStackExpr leaf_ids stack_ids],
411 envStackType leaf_ids stack,
414 mapDs make_branch leaves `thenDs` \ branches ->
415 dsLookupTyCon eitherTyConName `thenDs` \ either_con ->
416 dsLookupDataCon leftDataConName `thenDs` \ left_con ->
417 dsLookupDataCon rightDataConName `thenDs` \ right_con ->
419 left_id = HsVar (dataConWrapId left_con)
420 right_id = HsVar (dataConWrapId right_con)
421 left_expr ty1 ty2 e = HsApp (TyApp left_id [ty1, ty2]) e
422 right_expr ty1 ty2 e = HsApp (TyApp right_id [ty1, ty2]) e
424 -- Prefix each tuple with a distinct series of Left's and Right's,
425 -- in a balanced way, keeping track of the types.
427 merge_branches (fvs1, builds1, in_ty1, core_exp1)
428 (fvs2, builds2, in_ty2, core_exp2)
429 = (fvs1 `unionVarSet` fvs2,
430 map (left_expr in_ty1 in_ty2) builds1 ++
431 map (right_expr in_ty1 in_ty2) builds2,
432 mkTyConApp either_con [in_ty1, in_ty2],
433 do_choice ids in_ty1 in_ty2 res_ty core_exp1 core_exp2)
434 (fvs, leaves', sum_ty, core_choices) = foldb merge_branches branches
436 -- Replace the commands in the case with these tagged tuples,
437 -- yielding a TypecheckedHsExpr we can feed to dsExpr.
439 (_, matches') = mapAccumL (replaceLeavesMatch res_ty) leaves' matches
440 in_ty = envStackType env_ids stack
442 dsExpr (HsCase exp matches' src_loc) `thenDs` \ core_matches ->
443 returnDs(do_map_arrow ids in_ty sum_ty res_ty core_matches core_choices,
444 exprFreeVars core_exp `unionVarSet` fvs)
446 -- A, xs |- e :: Bool
447 -- A | xs1 |- c1 :: [ts] t
448 -- A | xs2 |- c2 :: [ts] t
449 -- ----------------------------------------
450 -- A | xs |- if e then c1 else c2 :: [ts] t
452 -- ---> arr (\ ((xs)*ts) ->
453 -- if e then Left ((xs1)*ts) else Right ((xs2)*ts)) >>>
456 dsCmd ids local_vars env_ids stack res_ty (HsIf cond then_cmd else_cmd src_loc)
457 = dsExpr cond `thenDs` \ core_cond ->
458 dsfixCmd ids local_vars stack res_ty then_cmd
459 `thenDs` \ (core_then, fvs_then, then_ids) ->
460 dsfixCmd ids local_vars stack res_ty else_cmd
461 `thenDs` \ (core_else, fvs_else, else_ids) ->
462 mapDs newSysLocalDs stack `thenDs` \ stack_ids ->
463 dsLookupTyCon eitherTyConName `thenDs` \ either_con ->
464 dsLookupDataCon leftDataConName `thenDs` \ left_con ->
465 dsLookupDataCon rightDataConName `thenDs` \ right_con ->
467 left_expr ty1 ty2 e = mkConApp left_con [Type ty1, Type ty2, e]
468 right_expr ty1 ty2 e = mkConApp right_con [Type ty1, Type ty2, e]
470 in_ty = envStackType env_ids stack
471 then_ty = envStackType then_ids stack
472 else_ty = envStackType else_ids stack
473 sum_ty = mkTyConApp either_con [then_ty, else_ty]
475 matchEnvStack env_ids stack_ids
476 (mkIfThenElse core_cond
477 (left_expr then_ty else_ty (buildEnvStack then_ids stack_ids))
478 (right_expr then_ty else_ty (buildEnvStack else_ids stack_ids)))
479 `thenDs` \ core_if ->
480 returnDs(do_map_arrow ids in_ty sum_ty res_ty
482 (do_choice ids then_ty else_ty res_ty core_then core_else),
483 exprFreeVars core_cond `unionVarSet` fvs_then `unionVarSet` fvs_else)
485 -- A | ys |- c :: [ts] t
486 -- ----------------------------------
487 -- A | xs |- let binds in c :: [ts] t
489 -- ---> arr (\ ((xs)*ts) -> let binds in ((ys)*ts)) >>> c
491 dsCmd ids local_vars env_ids stack res_ty (HsLet binds body)
493 defined_vars = mkVarSet (collectHsBinders binds)
494 local_vars' = local_vars `unionVarSet` defined_vars
496 dsfixCmd ids local_vars' stack res_ty body
497 `thenDs` \ (core_body, free_vars, env_ids') ->
498 mapDs newSysLocalDs stack `thenDs` \ stack_ids ->
499 -- build a new environment, plus the stack, using the let bindings
500 dsLet binds (buildEnvStack env_ids' stack_ids)
501 `thenDs` \ core_binds ->
502 -- match the old environment and stack against the input
503 matchEnvStack env_ids stack_ids core_binds
504 `thenDs` \ core_map ->
505 returnDs (do_map_arrow ids
506 (envStackType env_ids stack)
507 (envStackType env_ids' stack)
511 exprFreeVars core_binds `intersectVarSet` local_vars)
513 dsCmd ids local_vars env_ids [] res_ty (HsDo ctxt stmts _ _ src_loc)
514 = dsCmdDo ids local_vars env_ids res_ty stmts
516 -- A |- e :: forall e. a1 (e*ts1) t1 -> ... an (e*tsn) tn -> a (e*ts) t
517 -- A | xs |- ci :: [tsi] ti
518 -- -----------------------------------
519 -- A | xs |- (|e|) c1 ... cn :: [ts] t ---> e [t_xs] c1 ... cn
521 dsCmd ids local_vars env_ids _stack _res_ty (HsArrForm op _ args _)
523 env_ty = tupleType env_ids
525 dsExpr op `thenDs` \ core_op ->
526 mapAndUnzipDs (dsTrimCmdArg local_vars env_ids) args
527 `thenDs` \ (core_args, fv_sets) ->
528 returnDs (mkApps (App core_op (Type env_ty)) core_args,
529 unionVarSets fv_sets)
531 -- A | ys |- c :: [ts] t (ys <= xs)
532 -- ---------------------
533 -- A | xs |- c :: [ts] t ---> arr_ts (\ (xs) -> (ys)) >>> c
536 :: IdSet -- set of local vars available to this command
537 -> [Id] -- list of vars in the input to this command
538 -> TypecheckedHsCmdTop -- command argument to desugar
539 -> DsM (CoreExpr, -- desugared expression
540 IdSet) -- set of local vars that occur free
541 dsTrimCmdArg local_vars env_ids (HsCmdTop cmd stack cmd_ty ids)
542 = mkCmdEnv ids `thenDs` \ meth_ids ->
543 dsfixCmd meth_ids local_vars stack cmd_ty cmd
544 `thenDs` \ (core_cmd, free_vars, env_ids') ->
545 mapDs newSysLocalDs stack `thenDs` \ stack_ids ->
546 matchEnvStack env_ids stack_ids (buildEnvStack env_ids' stack_ids)
547 `thenDs` \ trim_code ->
549 in_ty = envStackType env_ids stack
550 in_ty' = envStackType env_ids' stack
551 arg_code = if env_ids' == env_ids then core_cmd else
552 do_map_arrow meth_ids in_ty in_ty' cmd_ty trim_code core_cmd
554 returnDs (bindCmdEnv meth_ids arg_code, free_vars)
556 -- Given A | xs |- c :: [ts] t, builds c with xs fed back.
557 -- Typically needs to be prefixed with arr (\p -> ((xs)*ts))
560 :: DsCmdEnv -- arrow combinators
561 -> IdSet -- set of local vars available to this command
562 -> [Type] -- type of the stack
563 -> Type -- return type of the command
564 -> TypecheckedHsCmd -- command to desugar
565 -> DsM (CoreExpr, -- desugared expression
566 IdSet, -- set of local vars that occur free
567 [Id]) -- set as a list, fed back
568 dsfixCmd ids local_vars stack cmd_ty cmd
569 = fixDs (\ ~(_,_,env_ids') ->
570 dsCmd ids local_vars env_ids' stack cmd_ty cmd
571 `thenDs` \ (core_cmd, free_vars) ->
572 returnDs (core_cmd, free_vars, varSetElems free_vars))
576 Translation of command judgements of the form
578 A | xs |- do { ss } :: [] t
582 dsCmdDo :: DsCmdEnv -- arrow combinators
583 -> IdSet -- set of local vars available to this statement
584 -> [Id] -- list of vars in the input to this statement
585 -- This is typically fed back,
586 -- so don't pull on it too early
587 -> Type -- return type of the statement
588 -> [TypecheckedStmt] -- statements to desugar
589 -> DsM (CoreExpr, -- desugared expression
590 IdSet) -- set of local vars that occur free
592 -- A | xs |- c :: [] t
593 -- --------------------------
594 -- A | xs |- do { c } :: [] t
596 dsCmdDo ids local_vars env_ids res_ty [ResultStmt cmd _locn]
597 = dsCmd ids local_vars env_ids [] res_ty cmd
599 dsCmdDo ids local_vars env_ids res_ty (stmt:stmts)
601 bound_vars = mkVarSet (collectStmtBinders stmt)
602 local_vars' = local_vars `unionVarSet` bound_vars
604 fixDs (\ ~(_,_,env_ids') ->
605 dsCmdDo ids local_vars' env_ids' res_ty stmts
606 `thenDs` \ (core_stmts, fv_stmts) ->
607 returnDs (core_stmts, fv_stmts, varSetElems fv_stmts))
608 `thenDs` \ (core_stmts, fv_stmts, env_ids') ->
609 dsCmdStmt ids local_vars env_ids env_ids' stmt
610 `thenDs` \ (core_stmt, fv_stmt) ->
611 returnDs (do_compose ids
620 :: DsCmdEnv -- arrow combinators
621 -> IdSet -- set of local vars available to this statement
622 -> [Id] -- list of vars in the input to this statement
623 -- This is typically fed back,
624 -- so don't pull on it too early
625 -> [Id] -- list of vars in the output of this statement
626 -> TypecheckedStmt -- statement to desugar
627 -> DsM (CoreExpr, -- desugared expression
628 IdSet) -- set of local vars that occur free
630 -- A | xs1 |- c :: [] t
631 -- A | xs' |- do { ss } :: [] t
632 -- ------------------------------
633 -- A | xs |- do { c; ss } :: [] t
635 -- ---> arr (\ (xs) -> ((xs1),(xs'))) >>> first c >>>
638 dsCmdStmt ids local_vars env_ids out_ids (ExprStmt cmd c_ty locn)
639 = dsfixCmd ids local_vars [] c_ty cmd
640 `thenDs` \ (core_cmd, fv_cmd, env_ids1) ->
641 matchEnvStack env_ids []
642 (mkCorePairExpr (mkTupleExpr env_ids1) (mkTupleExpr out_ids))
643 `thenDs` \ core_mux ->
645 in_ty = tupleType env_ids
646 in_ty1 = tupleType env_ids1
647 out_ty = tupleType out_ids
648 before_c_ty = mkCorePairTy in_ty1 out_ty
649 after_c_ty = mkCorePairTy c_ty out_ty
651 mkSndExpr c_ty out_ty `thenDs` \ snd_fn ->
652 returnDs (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
653 do_compose ids before_c_ty after_c_ty out_ty
654 (do_first ids in_ty1 c_ty out_ty core_cmd) $
655 do_arr ids after_c_ty out_ty snd_fn,
656 fv_cmd `unionVarSet` mkVarSet out_ids)
659 -- A | xs1 |- c :: [] t
660 -- A | xs' |- do { ss } :: [] t xs2 = xs' - defs(p)
661 -- -----------------------------------
662 -- A | xs |- do { p <- c; ss } :: [] t
664 -- ---> arr (\ (xs) -> ((xs1),(xs2))) >>> first c >>>
665 -- arr (\ (p, (xs2)) -> (xs')) >>> ss
667 -- It would be simpler and more consistent to do this using second,
668 -- but that's likely to be defined in terms of first.
670 dsCmdStmt ids local_vars env_ids out_ids (BindStmt pat cmd locn)
671 = dsfixCmd ids local_vars [] (hsPatType pat) cmd
672 `thenDs` \ (core_cmd, fv_cmd, env_ids1) ->
674 pat_vars = mkVarSet (collectPatBinders pat)
675 env_ids2 = varSetElems (mkVarSet out_ids `minusVarSet` pat_vars)
678 -- multiplexing function
679 -- \ (xs) -> ((xs1),(xs2))
681 matchEnvStack env_ids []
682 (mkCorePairExpr (mkTupleExpr env_ids1) (mkTupleExpr env_ids2))
683 `thenDs` \ core_mux ->
685 -- projection function
686 -- \ (p, (xs2)) -> (zs)
688 selectMatchVar pat `thenDs` \ pat_id ->
689 newSysLocalDs (tupleType env_ids2) `thenDs` \ env_id ->
690 getUniqSupplyDs `thenDs` \ uniqs ->
692 pair_ids = [pat_id, env_id]
693 after_c_ty = tupleType pair_ids
694 out_ty = tupleType out_ids
695 body_expr = coreCaseTuple uniqs env_id env_ids2 (mkTupleExpr out_ids)
697 mkFailExpr (StmtCtxt DoExpr) out_ty `thenDs` \ fail_expr ->
698 matchSimply (Var pat_id) (StmtCtxt DoExpr) pat body_expr fail_expr
699 `thenDs` \ match_code ->
700 newSysLocalDs after_c_ty `thenDs` \ pair_id ->
702 proj_expr = Lam pair_id (coreCaseSmallTuple pair_id pair_ids match_code)
705 -- put it all togther
707 pat_ty = hsPatType pat
708 in_ty = tupleType env_ids
709 in_ty1 = tupleType env_ids1
710 in_ty2 = tupleType env_ids2
711 before_c_ty = mkCorePairTy in_ty1 in_ty2
713 returnDs (do_map_arrow ids in_ty before_c_ty out_ty core_mux $
714 do_compose ids before_c_ty after_c_ty out_ty
715 (do_first ids in_ty1 pat_ty in_ty2 core_cmd) $
716 do_arr ids after_c_ty out_ty proj_expr,
717 fv_cmd `unionVarSet` (mkVarSet out_ids `minusVarSet` pat_vars))
719 -- A | xs' |- do { ss } :: [] t
720 -- --------------------------------------
721 -- A | xs |- do { let binds; ss } :: [] t
723 -- ---> arr (\ (xs) -> let binds in (xs')) >>> ss
725 dsCmdStmt ids local_vars env_ids out_ids (LetStmt binds)
726 -- build a new environment using the let bindings
727 = dsLet binds (mkTupleExpr out_ids) `thenDs` \ core_binds ->
728 -- match the old environment against the input
729 matchEnvStack env_ids [] core_binds `thenDs` \ core_map ->
734 exprFreeVars core_binds `intersectVarSet` local_vars)
736 -- A | ys |- do { ss; returnA -< ((xs1), (ys2)) } :: [] ...
737 -- A | xs' |- do { ss' } :: [] t
738 -- ------------------------------------
739 -- A | xs |- do { rec ss; ss' } :: [] t
741 -- xs1 = xs' /\ defs(ss)
742 -- xs2 = xs' - defs(ss)
743 -- ys1 = ys - defs(ss)
744 -- ys2 = ys /\ defs(ss)
746 -- ---> arr (\(xs) -> ((ys1),(xs2))) >>>
747 -- first (loop (arr (\((ys1),~(ys2)) -> (ys)) >>> ss)) >>>
748 -- arr (\((xs1),(xs2)) -> (xs')) >>> ss'
750 dsCmdStmt ids local_vars env_ids out_ids' (RecStmt stmts later_ids rec_ids rhss)
752 rec_id_set = mkVarSet rec_ids
753 out_ids = varSetElems (mkVarSet later_ids `unionVarSet` rec_id_set)
754 out_ty = tupleType out_ids
755 local_vars' = local_vars `unionVarSet` rec_id_set
758 -- mk_pair_fn = \ (out_ids) -> ((later_ids),(rhss))
760 mapDs dsExpr rhss `thenDs` \ core_rhss ->
762 later_tuple = mkTupleExpr later_ids
763 later_ty = tupleType later_ids
764 rec_tuple = mkCoreTup core_rhss
765 rec_ty = tupleType rec_ids
766 out_pair = mkCoreTup [later_tuple, rec_tuple]
767 out_pair_ty = mkCoreTupTy [later_ty, rec_ty]
769 matchEnvStack out_ids [] out_pair
770 `thenDs` \ mk_pair_fn ->
772 dsfixCmdStmts ids local_vars' out_ids stmts
773 `thenDs` \ (core_stmts, fv_stmts, env_ids') ->
775 -- squash_pair_fn = \ ((env1_ids), ~(rec_ids)) -> (env_ids')
777 newSysLocalDs rec_ty `thenDs` \ rec_id ->
779 env1_id_set = fv_stmts `minusVarSet` rec_id_set
780 env1_ids = varSetElems env1_id_set
781 env1_ty = tupleType env1_ids
782 in_pair_ty = mkCoreTupTy [env1_ty, rec_ty]
783 core_body = mkCoreTup (map selectVar env_ids')
786 | v `elemVarSet` rec_id_set
787 = mkTupleSelector rec_ids v rec_id (Var rec_id)
790 matchEnvStack env1_ids [rec_id] core_body
791 `thenDs` \ squash_pair_fn ->
793 -- loop (arr squash_pair_fn >>> ss >>> arr mk_pair_fn)
796 env_ty' = tupleType env_ids'
797 core_loop = do_loop ids env1_ty later_ty rec_ty
798 (do_map_arrow ids in_pair_ty env_ty' out_pair_ty
800 (do_compose ids env_ty' out_ty out_pair_ty
802 (do_arr ids out_ty out_pair_ty mk_pair_fn)))
805 -- pre_loop_fn = \(env_ids) -> ((env1_ids),(env2_ids))
808 env_ty = tupleType env_ids
809 env2_id_set = mkVarSet out_ids' `minusVarSet` mkVarSet later_ids
810 env2_ids = varSetElems env2_id_set
811 env2_ty = tupleType env2_ids
812 pre_pair_ty = mkCoreTupTy [env1_ty, env2_ty]
813 pre_loop_body = mkCoreTup [mkTupleExpr env1_ids, mkTupleExpr env2_ids]
816 matchEnvStack env_ids [] pre_loop_body
817 `thenDs` \ pre_loop_fn ->
819 -- post_loop_fn = \((later_ids),(env2_ids)) -> (out_ids')
821 getUniqSupplyDs `thenDs` \ uniqs ->
822 newSysLocalDs env2_ty `thenDs` \ env2_id ->
824 out_ty' = tupleType out_ids'
825 post_pair_ty = mkCoreTupTy [later_ty, env2_ty]
826 post_loop_body = coreCaseTuple uniqs env2_id env2_ids (mkTupleExpr out_ids')
828 matchEnvStack later_ids [env2_id] post_loop_body
829 `thenDs` \ post_loop_fn ->
831 -- arr pre_loop_fn >>> first (loop (...)) >>> arr post_loop_fn
834 core_body = do_map_arrow ids env_ty pre_pair_ty out_ty'
836 (do_compose ids pre_pair_ty post_pair_ty out_ty'
837 (do_first ids env1_ty later_ty env2_ty
839 (do_arr ids post_pair_ty out_ty'
842 returnDs (core_body, env1_id_set `unionVarSet` env2_id_set)
845 A sequence of statements (as is a rec) is desugared to an arrow between
850 :: DsCmdEnv -- arrow combinators
851 -> IdSet -- set of local vars available to this statement
852 -> [Id] -- output vars of these statements
853 -> [TypecheckedStmt] -- statements to desugar
854 -> DsM (CoreExpr, -- desugared expression
855 IdSet, -- set of local vars that occur free
858 dsfixCmdStmts ids local_vars out_ids stmts
859 = fixDs (\ ~(_,_,env_ids) ->
860 dsCmdStmts ids local_vars env_ids out_ids stmts
861 `thenDs` \ (core_stmts, fv_stmts) ->
862 returnDs (core_stmts, fv_stmts, varSetElems fv_stmts))
865 :: DsCmdEnv -- arrow combinators
866 -> IdSet -- set of local vars available to this statement
867 -> [Id] -- list of vars in the input to these statements
868 -> [Id] -- output vars of these statements
869 -> [TypecheckedStmt] -- statements to desugar
870 -> DsM (CoreExpr, -- desugared expression
871 IdSet) -- set of local vars that occur free
873 dsCmdStmts ids local_vars env_ids out_ids [stmt]
874 = dsCmdStmt ids local_vars env_ids out_ids stmt
876 dsCmdStmts ids local_vars env_ids out_ids (stmt:stmts)
878 bound_vars = mkVarSet (collectStmtBinders stmt)
879 local_vars' = local_vars `unionVarSet` bound_vars
881 dsfixCmdStmts ids local_vars' out_ids stmts
882 `thenDs` \ (core_stmts, fv_stmts, env_ids') ->
883 dsCmdStmt ids local_vars env_ids env_ids' stmt
884 `thenDs` \ (core_stmt, fv_stmt) ->
885 returnDs (do_compose ids
895 Match a list of expressions against a list of patterns, left-to-right.
898 matchSimplys :: [CoreExpr] -- Scrutinees
899 -> TypecheckedMatchContext -- Match kind
900 -> [TypecheckedPat] -- Patterns they should match
901 -> CoreExpr -- Return this if they all match
902 -> CoreExpr -- Return this if they don't
904 matchSimplys [] _ctxt [] result_expr fail_expr = returnDs result_expr
905 matchSimplys (exp:exps) ctxt (pat:pats) result_expr fail_expr
906 = matchSimplys exps ctxt pats result_expr fail_expr
907 `thenDs` \ match_code ->
908 matchSimply exp ctxt pat match_code fail_expr
913 -- list of leaf expressions, with set of variables bound in each
914 leavesMatch :: TypecheckedMatch -> [(TypecheckedHsExpr, IdSet)]
915 leavesMatch (Match pats _ (GRHSs grhss binds _ty))
917 defined_vars = mkVarSet (collectPatsBinders pats) `unionVarSet`
918 mkVarSet (collectHsBinders binds)
920 [(expr, mkVarSet (collectStmtsBinders stmts) `unionVarSet` defined_vars) |
921 GRHS stmts _locn <- grhss,
922 let ResultStmt expr _ = last stmts]
924 -- Replace the leaf commands in a match
927 :: Type -- new result type
928 -> [TypecheckedHsExpr] -- replacement leaf expressions of that type
929 -> TypecheckedMatch -- the matches of a case command
930 -> ([TypecheckedHsExpr],-- remaining leaf expressions
931 TypecheckedMatch) -- updated match
932 replaceLeavesMatch res_ty leaves (Match pat mt (GRHSs grhss binds _ty))
934 (leaves', grhss') = mapAccumL (replaceLeavesGRHS res_ty) leaves grhss
936 (leaves', Match pat mt (GRHSs grhss' binds res_ty))
939 :: Type -- new result type
940 -> [TypecheckedHsExpr] -- replacement leaf expressions of that type
941 -> TypecheckedGRHS -- rhss of a case command
942 -> ([TypecheckedHsExpr],-- remaining leaf expressions
943 TypecheckedGRHS) -- updated GRHS
944 replaceLeavesGRHS res_ty (leaf:leaves) (GRHS stmts srcloc)
945 = (leaves, GRHS (init stmts ++ [ResultStmt leaf srcloc]) srcloc)
949 Balanced fold of a non-empty list.
952 foldb :: (a -> a -> a) -> [a] -> a
953 foldb f [] = error "foldb of empty list"
955 foldb f xs = foldb f (fold_pairs xs)
959 fold_pairs (x1:x2:xs) = f x1 x2:fold_pairs xs