Hermes: A Tutorial and Reference Manual - Researcher - IBM
Hermes: A Tutorial and Reference Manual - Researcher - IBM
Hermes: A Tutorial and Reference Manual - Researcher - IBM
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462.7.TheWindowManager callCurrentWindow.InputToWindow(DispatchCM.Line);<br />
ofanyothertypecontainingthesetypes(suchasarecordcontainingan <strong>and</strong>callmessagetypefamiliesarenotcopyable.Variablesofthesetypes,or selectorexpressiontocopyanelementfromthetableintoavariable.We shouldpointoutonesituationinwhichthisdoesnotwork.Theinputport Thisprogramillustratesonewaytolookupsomethinginatable|usea endblock; on(NotFound) returnDispatchCMexceptionNotFound; returnDispatchCM;<br />
inputportoratablecontainingacallmessage)cannotbecopied.Todoa tablelookupwhenthetableelementscannotbecopied,usetheinspect statement.Hereisthesameprogramfragmentrewrittenwiththeinspect<br />
blockbegin receiveDispatchCMfromDispatch; inspectWinCreatedWindows[DispatchCM.WindowName] begin<br />
anobjectofanydatatype,becausetheproblematicoperationsareillegal elementoftableCreatedWindows.<strong>Hermes</strong>doesnotallowmakingcopies returnwouldbecomecomplex.Howeverconstantcopiesmaybemadeof ofinputports<strong>and</strong>callmessages,becausethesemanticsofreceive<strong>and</strong> TheinspectstatementassignsWfromaconstantcopyoftheselected on(NotFound) endblock; endinspect; callW.InputToWindow(DispatchCM.Line);<br />
non-copyablecases. Thatway,youwillnothavetousetwodierentstylesforthecopyable<strong>and</strong> whenappliedtoconstants. fortablelookupallthetime,evenwhenthetableelementsarecopyable. declareCurrentWindow.Butintheversionusinginspect,youdon'twrite oftableCreatedWindows.Youmaywishtousetheinspectstatement newscopeinwhichWisdeclaredtohavetypeWindow|theelementtype aseparatedeclarationforthevariableW.Theinspectstatementdenesa Theinspectstatementselectsexactlyoneelement(orelseraisesan Intheprogramfragmentwrittenwithoutinspect,itisnecessaryto<br />
eachelementofatablewhichsatisestheselectorpredicate.(Thismaybe forstatementiterativelyexecutesthestatementswithinitsbodyoncefor exception).Toselectallelements,iteratively,useaforstatement.The example,hereisapieceofcodewhichprintsthenamesofalltheactive zerotimesifthetableisemptyorifnoelementsatisestheselector.)For windows: forWindowinCreatedWindowswhere('true')
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