2 % (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
4 \section[MkIface]{Print an interface for a module}
8 startIface, endIface, ifaceDecls
11 #include "HsVersions.h"
13 import IO ( Handle, hPutStr, openFile,
14 hClose, hPutStrLn, IOMode(..) )
17 import BasicTypes ( Fixity(..), FixityDirection(..), NewOrData(..) )
19 import RnEnv ( availName )
21 import TcInstUtil ( InstInfo(..) )
24 import Id ( Id, idType, idInfo, omitIfaceSigForId, isUserExportedId,
29 import DataCon ( StrictnessMark(..), dataConSig, dataConFieldLabels, dataConStrictMarks )
30 import IdInfo ( IdInfo, StrictnessInfo(..), ArityInfo, InlinePragInfo(..), inlinePragInfo,
31 arityInfo, ppArityInfo, arityLowerBound,
32 strictnessInfo, ppStrictnessInfo, isBottomingStrictness,
33 cafInfo, ppCafInfo, specInfo,
34 cprInfo, ppCprInfo, pprInlinePragInfo,
36 workerExists, workerInfo, ppWorkerInfo
38 import CoreSyn ( CoreExpr, CoreBind, Bind(..), rulesRules, rulesRhsFreeVars )
39 import CoreFVs ( exprSomeFreeVars, ruleSomeLhsFreeVars, ruleSomeFreeVars )
40 import CoreUnfold ( calcUnfoldingGuidance, okToUnfoldInHiFile, couldBeSmallEnoughToInline )
41 import Module ( moduleString, pprModule, pprModuleName )
42 import Name ( isLocallyDefined, isWiredInName, nameRdrName, nameModule,
45 import OccName ( OccName, pprOccName )
46 import TyCon ( TyCon, getSynTyConDefn, isSynTyCon, isNewTyCon, isAlgTyCon,
47 tyConTheta, tyConTyVars, tyConDataCons
49 import Class ( Class, classExtraBigSig )
50 import FieldLabel ( fieldLabelName, fieldLabelType )
51 import Type ( mkSigmaTy, splitSigmaTy, mkDictTy, tidyTopType,
52 deNoteType, classesToPreds,
53 Type, ThetaType, PredType(..), ClassContext
57 import PprCore ( pprIfaceUnfolding, pprCoreRule )
58 import FunDeps ( pprFundeps )
59 import Rules ( pprProtoCoreRule, ProtoCoreRule(..) )
61 import Bag ( bagToList, isEmptyBag )
62 import Maybes ( catMaybes, maybeToBool )
63 import FiniteMap ( emptyFM, addToFM, addToFM_C, fmToList, FiniteMap )
64 import UniqFM ( lookupUFM, listToUFM )
65 import UniqSet ( uniqSetToList )
66 import Util ( sortLt, mapAccumL )
71 We have a function @startIface@ to open the output file and put
72 (something like) ``interface Foo'' in it. It gives back a handle
73 for subsequent additions to the interface file.
75 We then have one-function-per-block-of-interface-stuff, e.g.,
76 @ifaceExportList@ produces the @__exports__@ section; it appends
77 to the handle provided by @startIface@.
79 NOTE: ALWAYS remember that ghc-iface.lprl rewrites the interface file,
80 so you have to keep it in synch with the code below. Otherwise you'll
81 lose the happiest years of your life, believe me... -- SUP
84 startIface :: Module -> InterfaceDetails
85 -> IO (Maybe Handle) -- Nothing <=> don't do an interface
87 ifaceDecls :: Maybe Handle
90 -> [Id] -- Ids used at code-gen time; they have better pragma info!
91 -> [CoreBind] -- In dependency order, later depend on earlier
92 -> [ProtoCoreRule] -- Rules
96 endIface :: Maybe Handle -> IO ()
100 startIface mod (InterfaceDetails has_orphans import_usages (ExportEnv avails fixities _) _)
101 = case opt_ProduceHi of
102 Nothing -> return Nothing ; -- not producing any .hi file
105 if_hdl <- openFile fn WriteMode
106 hPutStr if_hdl ("__interface " ++ moduleString mod)
107 hPutStr if_hdl (' ' : show (opt_HiVersion :: Int) ++ orphan_indicator)
108 hPutStrLn if_hdl " where"
109 ifaceExports if_hdl avails
110 ifaceImports if_hdl import_usages
111 ifaceFixities if_hdl fixities
114 orphan_indicator | has_orphans = " !"
117 endIface Nothing = return ()
118 endIface (Just if_hdl) = hPutStr if_hdl "\n" >> hClose if_hdl
123 ifaceDecls Nothing tycons classes inst_info final_ids simplified rules _ = return ()
124 ifaceDecls (Just hdl)
129 orphan_rules -- Rules defined locally for an Id that is *not* defined locally
131 | null_decls = return ()
132 -- You could have a module with just (re-)exports/instances in it
134 = ifaceClasses hdl classes >>
135 ifaceInstances hdl inst_infos >>= \ inst_ids ->
136 ifaceTyCons hdl tycons >>
137 ifaceBinds hdl (inst_ids `unionVarSet` orphan_rule_ids)
138 final_ids binds >>= \ emitted_ids ->
139 ifaceRules hdl orphan_rules emitted_ids >>
140 ifaceDeprecations hdl deprecations
142 orphan_rule_ids = unionVarSets [ ruleSomeFreeVars interestingId rule
143 | ProtoCoreRule _ _ rule <- orphan_rules]
145 null_decls = null binds &&
148 isEmptyBag inst_infos &&
154 ifaceImports :: Handle -> VersionInfo Name -> IO ()
155 ifaceImports if_hdl import_usages
156 = hPutCol if_hdl upp_uses (sortLt lt_imp_vers import_usages)
158 upp_uses (m, mv, has_orphans, whats_imported)
159 = hsep [ptext SLIT("import"), pprModuleName m,
161 upp_import_versions whats_imported
164 pp_orphan | has_orphans = ptext SLIT("!")
167 -- Importing the whole module is indicated by an empty list
168 upp_import_versions Everything = empty
170 -- For imported versions we do print the version number
171 upp_import_versions (Specifically nvs)
172 = dcolon <+> hsep [ hsep [ppr_unqual_name n, int v] | (n,v) <- sort_versions nvs ]
174 {- SUP: What's this??
175 ifaceModuleDeps if_hdl [] = return ()
176 ifaceModuleDeps if_hdl mod_deps
178 lines = map ppr_mod_dep mod_deps
179 ppr_mod_dep (mod, contains_orphans)
180 | contains_orphans = pprModuleName mod <+> ptext SLIT("!")
181 | otherwise = pprModuleName mod
183 printForIface if_hdl (ptext SLIT("__depends") <+> vcat lines <> ptext SLIT(" ;")) >>
187 ifaceExports :: Handle -> Avails -> IO ()
188 ifaceExports if_hdl [] = return ()
189 ifaceExports if_hdl avails
190 = hPutCol if_hdl do_one_module (fmToList export_fm)
192 -- Sort them into groups by module
193 export_fm :: FiniteMap Module [AvailInfo]
194 export_fm = foldr insert emptyFM avails
196 insert avail efm = addToFM_C (++) efm mod [avail]
198 mod = nameModule (availName avail)
200 -- Print one module's worth of stuff
201 do_one_module :: (Module, [AvailInfo]) -> SDoc
202 do_one_module (mod_name, avails@(avail1:_))
203 = ptext SLIT("__export ") <>
204 hsep [pprModule mod_name,
205 hsep (map upp_avail (sortLt lt_avail avails))
208 ifaceFixities :: Handle -> Fixities -> IO ()
209 ifaceFixities if_hdl [] = return ()
210 ifaceFixities if_hdl fixities
211 = hPutCol if_hdl upp_fixity fixities
213 ifaceRules :: Handle -> [ProtoCoreRule] -> IdSet -> IO ()
214 ifaceRules if_hdl rules emitted
215 | null orphan_rule_pretties && null local_id_pretties
218 = printForIface if_hdl (vcat [
219 ptext SLIT("{-## __R"),
220 vcat orphan_rule_pretties,
221 vcat local_id_pretties,
225 orphan_rule_pretties = [ pprCoreRule (Just fn) rule
226 | ProtoCoreRule _ fn rule <- rules
228 local_id_pretties = [ pprCoreRule (Just fn) rule
229 | fn <- varSetElems emitted,
230 rule <- rulesRules (getIdSpecialisation fn),
231 all (`elemVarSet` emitted) (varSetElems (ruleSomeLhsFreeVars interestingId rule))
232 -- Spit out a rule only if all its lhs free vars are emitted
235 ifaceDeprecations :: Handle -> [Deprecation Name] -> IO ()
236 ifaceDeprecations if_hdl [] = return ()
237 ifaceDeprecations if_hdl deprecations
238 = printForIface if_hdl (vcat [
239 ptext SLIT("{-## __D"),
240 vcat [ pprIfaceDeprec d <> semi | d <- deprecations ],
244 pprIfaceDeprec (DeprecMod txt) = doubleQuotes (ppr txt)
245 pprIfaceDeprec (DeprecName n txt) = ppr n <+> doubleQuotes (ppr txt)
248 %************************************************************************
250 \subsection{Instance declarations}
252 %************************************************************************
256 ifaceInstances :: Handle -> Bag InstInfo -> IO IdSet -- The IdSet is the needed dfuns
257 ifaceInstances if_hdl inst_infos
258 | null togo_insts = return emptyVarSet
259 | otherwise = hPutCol if_hdl pp_inst (sortLt lt_inst togo_insts) >>
262 togo_insts = filter is_togo_inst (bagToList inst_infos)
263 needed_ids = mkVarSet [dfun_id | InstInfo _ _ _ _ dfun_id _ _ _ <- togo_insts]
264 is_togo_inst (InstInfo _ _ _ _ dfun_id _ _ _) = isLocallyDefined dfun_id
267 lt_inst (InstInfo _ _ _ _ dfun_id1 _ _ _)
268 (InstInfo _ _ _ _ dfun_id2 _ _ _)
269 = getOccName dfun_id1 < getOccName dfun_id2
270 -- The dfuns are assigned names df1, df2, etc, in order of original textual
271 -- occurrence, and this makes as good a sort order as any
274 pp_inst (InstInfo clas tvs tys theta dfun_id _ _ _)
276 -- The deNoteType is very important. It removes all type
277 -- synonyms from the instance type in interface files.
278 -- That in turn makes sure that when reading in instance decls
279 -- from interface files that the 'gating' mechanism works properly.
280 -- Otherwise you could have
281 -- type Tibble = T Int
282 -- instance Foo Tibble where ...
283 -- and this instance decl wouldn't get imported into a module
284 -- that mentioned T but not Tibble.
285 forall_ty = mkSigmaTy tvs (classesToPreds theta)
286 (deNoteType (mkDictTy clas tys))
287 renumbered_ty = tidyTopType forall_ty
289 hcat [ptext SLIT("instance "), pprType renumbered_ty,
290 ptext SLIT(" = "), ppr_unqual_name dfun_id, semi]
294 %************************************************************************
296 \subsection{Printing values}
298 %************************************************************************
301 ifaceId :: (Id -> IdInfo) -- This function "knows" the extra info added
302 -- by the STG passes. Sigh
304 -> IdSet -- Set of Ids that are needed by earlier interface
305 -- file emissions. If the Id isn't in this set, and isn't
306 -- exported, there's no need to emit anything
307 -> Bool -- True <=> recursive, so don't print unfolding
309 -> CoreExpr -- The Id's right hand side
310 -> Maybe (SDoc, IdSet) -- The emitted stuff, plus any *extra* needed Ids
312 ifaceId get_idinfo needed_ids is_rec id rhs
313 | not (id `elemVarSet` needed_ids || -- Needed [no id in needed_ids has omitIfaceSigForId]
314 (isUserExportedId id && not (omitIfaceSigForId id))) -- or exported and not to be omitted
315 = Nothing -- Well, that was easy!
317 ifaceId get_idinfo needed_ids is_rec id rhs
318 = ASSERT2( arity_matches_strictness, ppr id )
319 Just (hsep [sig_pretty, prag_pretty, char ';'], new_needed_ids)
321 core_idinfo = idInfo id
322 stg_idinfo = get_idinfo id
324 ty_pretty = pprType (idType id)
325 sig_pretty = hsep [ppr (getOccName id), dcolon, ty_pretty]
328 | opt_OmitInterfacePragmas = empty
329 | otherwise = hsep [ptext SLIT("{-##"),
338 ------------ Arity --------------
339 arity_info = arityInfo stg_idinfo
340 arity_pretty = ppArityInfo arity_info
342 ------------ Caf Info --------------
343 caf_pretty = ppCafInfo (cafInfo stg_idinfo)
345 ------------ CPR Info --------------
346 cpr_pretty = ppCprInfo (cprInfo core_idinfo)
348 ------------ Strictness --------------
349 strict_info = strictnessInfo core_idinfo
350 bottoming_fn = isBottomingStrictness strict_info
351 strict_pretty = ppStrictnessInfo strict_info
353 ------------ Worker --------------
354 work_info = workerInfo core_idinfo
355 has_worker = workerExists work_info
356 wrkr_pretty = ppWorkerInfo work_info
357 Just work_id = work_info
360 ------------ Occ info --------------
361 loop_breaker = case occInfo core_idinfo of
362 IAmALoopBreaker -> True
365 ------------ Unfolding --------------
366 inline_pragma = inlinePragInfo core_idinfo
367 dont_inline = case inline_pragma of
368 IMustNotBeINLINEd False Nothing -> True -- Unconditional NOINLINE
372 unfold_pretty | show_unfold = ptext SLIT("__U") <> pprInlinePragInfo inline_pragma <+> pprIfaceUnfolding rhs
375 show_unfold = not has_worker && -- Not unnecessary
376 not bottoming_fn && -- Not necessary
379 rhs_is_small && -- Small enough
380 okToUnfoldInHiFile rhs -- No casms etc
382 rhs_is_small = couldBeSmallEnoughToInline (calcUnfoldingGuidance opt_UF_HiFileThreshold rhs)
384 ------------ Specialisations --------------
385 spec_info = specInfo core_idinfo
387 ------------ Extra free Ids --------------
388 new_needed_ids | opt_OmitInterfacePragmas = emptyVarSet
389 | otherwise = worker_ids `unionVarSet`
390 unfold_ids `unionVarSet`
393 worker_ids | has_worker && interestingId work_id = unitVarSet work_id
394 -- Conceivably, the worker might come from
396 | otherwise = emptyVarSet
398 spec_ids = filterVarSet interestingId (rulesRhsFreeVars spec_info)
400 unfold_ids | show_unfold = find_fvs rhs
401 | otherwise = emptyVarSet
403 find_fvs expr = exprSomeFreeVars interestingId expr
405 ------------ Sanity checking --------------
406 -- The arity of a wrapper function should match its strictness,
407 -- or else an importing module will get very confused indeed.
408 -- [later: actually all that is necessary is for strictness to exceed arity]
409 arity_matches_strictness
412 StrictnessInfo ds _ -> length ds >= arityLowerBound arity_info
415 interestingId id = isId id && isLocallyDefined id &&
416 not (omitIfaceSigForId id)
421 -> IdSet -- These Ids are needed already
422 -> [Id] -- Ids used at code-gen time; they have better pragma info!
423 -> [CoreBind] -- In dependency order, later depend on earlier
424 -> IO IdSet -- Set of Ids actually spat out
426 ifaceBinds hdl needed_ids final_ids binds
427 = mapIO (printForIface hdl) (bagToList pretties) >>
431 final_id_map = listToUFM [(id,id) | id <- final_ids]
432 get_idinfo id = case lookupUFM final_id_map id of
433 Just id' -> idInfo id'
434 Nothing -> pprTrace "ifaceBinds not found:" (ppr id) $
437 (pretties, emitted) = go needed_ids (reverse binds) emptyBag emptyVarSet
438 -- Reverse so that later things will
439 -- provoke earlier ones to be emitted
440 go needed [] pretties emitted
441 | not (isEmptyVarSet needed) = pprTrace "ifaceBinds: free vars:"
442 (sep (map ppr (varSetElems needed)))
444 | otherwise = (pretties, emitted)
446 go needed (NonRec id rhs : binds) pretties emitted
447 = case ifaceId get_idinfo needed False id rhs of
448 Nothing -> go needed binds pretties emitted
449 Just (pretty, extras) -> let
450 needed' = (needed `unionVarSet` extras) `delVarSet` id
451 -- 'extras' can include the Id itself via a rule
452 emitted' = emitted `extendVarSet` id
454 go needed' binds (pretty `consBag` pretties) emitted'
456 -- Recursive groups are a bit more of a pain. We may only need one to
457 -- start with, but it may call out the next one, and so on. So we
458 -- have to look for a fixed point.
459 go needed (Rec pairs : binds) pretties emitted
460 = go needed' binds pretties' emitted'
462 (new_pretties, new_emitted, extras) = go_rec needed pairs
463 pretties' = new_pretties `unionBags` pretties
464 needed' = (needed `unionVarSet` extras) `minusVarSet` mkVarSet (map fst pairs)
465 emitted' = emitted `unionVarSet` new_emitted
467 go_rec :: IdSet -> [(Id,CoreExpr)] -> (Bag SDoc, IdSet, IdSet)
469 | null pretties = (emptyBag, emptyVarSet, emptyVarSet)
470 | otherwise = (more_pretties `unionBags` listToBag pretties,
471 more_emitted `unionVarSet` mkVarSet emitted,
472 more_extras `unionVarSet` extras)
474 maybes = map do_one pairs
475 emitted = [id | ((id,_), Just _) <- pairs `zip` maybes]
476 reduced_pairs = [pair | (pair, Nothing) <- pairs `zip` maybes]
477 (pretties, extras_s) = unzip (catMaybes maybes)
478 extras = unionVarSets extras_s
479 (more_pretties, more_emitted, more_extras) = go_rec extras reduced_pairs
481 do_one (id,rhs) = ifaceId get_idinfo needed True id rhs
485 %************************************************************************
487 \subsection{Random small things}
489 %************************************************************************
492 ifaceTyCons hdl tycons = hPutCol hdl upp_tycon (sortLt (<) (filter (for_iface_name . getName) tycons))
493 ifaceClasses hdl classes = hPutCol hdl upp_class (sortLt (<) (filter (for_iface_name . getName) classes))
495 for_iface_name name = isLocallyDefined name &&
496 not (isWiredInName name)
498 upp_tycon tycon = ifaceTyCon tycon
499 upp_class clas = ifaceClass clas
504 ifaceTyCon :: TyCon -> SDoc
507 = hsep [ ptext SLIT("type"),
509 pprTyVarBndrs tyvars,
515 (tyvars, ty) = getSynTyConDefn tycon
519 = hsep [ ptext keyword,
520 ppr_decl_class_context (tyConTheta tycon),
522 pprTyVarBndrs (tyConTyVars tycon),
524 hsep (punctuate (ptext SLIT(" | ")) (map ppr_con (tyConDataCons tycon))),
528 keyword | isNewTyCon tycon = SLIT("newtype")
529 | otherwise = SLIT("data")
531 tyvars = tyConTyVars tycon
535 = ASSERT( tycon == tycon1 && tyvars == tyvars1 )
536 hsep [ ppr_ex ex_tyvars ex_theta,
538 hsep (map ppr_arg_ty (strict_marks `zip` arg_tys))
542 = hsep [ ppr_ex ex_tyvars ex_theta,
544 braces $ hsep $ punctuate comma (map ppr_field (strict_marks `zip` field_labels))
547 (tyvars1, theta1, ex_tyvars, ex_theta, arg_tys, tycon1) = dataConSig data_con
548 field_labels = dataConFieldLabels data_con
549 strict_marks = dataConStrictMarks data_con
550 name = getName data_con
552 ppr_ex [] ex_theta = ASSERT( null ex_theta ) empty
553 ppr_ex ex_tvs ex_theta = ptext SLIT("__forall") <+> brackets (pprTyVarBndrs ex_tvs)
554 <+> pprIfaceClasses ex_theta <+> ptext SLIT("=>")
556 ppr_arg_ty (strict_mark, ty) = ppr_strict_mark strict_mark <> pprParendType ty
558 ppr_strict_mark NotMarkedStrict = empty
559 ppr_strict_mark (MarkedUnboxed _ _) = ptext SLIT("! ! ")
560 ppr_strict_mark MarkedStrict = ptext SLIT("! ")
562 ppr_field (strict_mark, field_label)
563 = hsep [ ppr (fieldLabelName field_label),
565 ppr_strict_mark strict_mark <> pprParendType (fieldLabelType field_label)
569 = pprPanic "pprIfaceTyDecl" (ppr tycon)
572 = hsep [ptext SLIT("class"),
573 ppr_decl_class_context sc_theta,
574 ppr clas, -- Print the name
575 pprTyVarBndrs clas_tyvars,
581 (clas_tyvars, clas_fds, sc_theta, _, op_stuff) = classExtraBigSig clas
583 pp_ops | null op_stuff = empty
584 | otherwise = hsep [ptext SLIT("where"),
585 braces (hsep (punctuate semi (map ppr_classop op_stuff)))
588 ppr_classop (sel_id, dm_id, explicit_dm)
589 = ASSERT( sel_tyvars == clas_tyvars)
590 hsep [ppr (getOccName sel_id),
591 if explicit_dm then equals else empty,
596 (sel_tyvars, _, op_ty) = splitSigmaTy (idType sel_id)
598 ppr_decl_context :: ThetaType -> SDoc
599 ppr_decl_context [] = empty
600 ppr_decl_context theta = pprIfaceTheta theta <+> ptext SLIT(" =>")
602 ppr_decl_class_context :: ClassContext -> SDoc
603 ppr_decl_class_context [] = empty
604 ppr_decl_class_context ctxt = pprIfaceClasses ctxt <+> ptext SLIT(" =>")
606 pprIfaceTheta :: ThetaType -> SDoc -- Use braces rather than parens in interface files
607 pprIfaceTheta [] = empty
608 pprIfaceTheta theta = braces (hsep (punctuate comma [pprIfacePred p | p <- theta]))
610 -- ZZ - not sure who uses this - i.e. whether IParams really show up or not
611 -- (it's not used to print normal value signatures)
612 pprIfacePred :: PredType -> SDoc
613 pprIfacePred (Class clas tys) = pprConstraint clas tys
614 pprIfacePred (IParam n ty) = char '?' <> ppr n <+> ptext SLIT("::") <+> ppr ty
616 pprIfaceClasses :: ClassContext -> SDoc
617 pprIfaceClasses [] = empty
618 pprIfaceClasses theta = braces (hsep (punctuate comma [pprConstraint c tys | (c,tys) <- theta]))
621 %************************************************************************
623 \subsection{Random small things}
625 %************************************************************************
627 When printing export lists, we print like this:
629 AvailTC C [C, x, y] C(x,y)
630 AvailTC C [x, y] C!(x,y) -- Exporting x, y but not C
633 upp_avail :: AvailInfo -> SDoc
634 upp_avail (Avail name) = pprOccName (getOccName name)
635 upp_avail (AvailTC name []) = empty
636 upp_avail (AvailTC name ns) = hcat [pprOccName (getOccName name), bang, upp_export ns']
638 bang | name `elem` ns = empty
639 | otherwise = char '|'
640 ns' = filter (/= name) ns
642 upp_export :: [Name] -> SDoc
643 upp_export [] = empty
644 upp_export names = braces (hsep (map (pprOccName . getOccName) names))
646 upp_fixity :: (Name, Fixity) -> SDoc
647 upp_fixity (name, fixity) = hsep [ptext SLIT("0"), ppr fixity, ppr name, semi]
648 -- Dummy version number!
650 ppr_unqual_name :: NamedThing a => a -> SDoc -- Just its occurrence name
651 ppr_unqual_name name = pprOccName (getOccName name)
655 %************************************************************************
657 \subsection{Comparisons}
659 %************************************************************************
662 The various sorts above simply prevent unnecessary "wobbling" when
663 things change that don't have to. We therefore compare lexically, not
667 lt_avail :: AvailInfo -> AvailInfo -> Bool
669 a1 `lt_avail` a2 = availName a1 `lt_name` availName a2
671 lt_name :: Name -> Name -> Bool
672 n1 `lt_name` n2 = nameRdrName n1 < nameRdrName n2
674 lt_lexical :: NamedThing a => a -> a -> Bool
675 lt_lexical a1 a2 = getName a1 `lt_name` getName a2
677 lt_imp_vers :: ImportVersion a -> ImportVersion a -> Bool
678 lt_imp_vers (m1,_,_,_) (m2,_,_,_) = m1 < m2
680 sort_versions vs = sortLt lt_vers vs
682 lt_vers :: LocalVersion Name -> LocalVersion Name -> Bool
683 lt_vers (n1,v1) (n2,v2) = n1 `lt_name` n2
692 hPutCol hdl fmt xs = mapIO (printForIface hdl . fmt) xs
694 mapIO :: (a -> IO b) -> [a] -> IO ()
695 mapIO f [] = return ()
696 mapIO f (x:xs) = f x >> mapIO f xs