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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inspectanelementormergeatableataparticularposition,locatethe subtablefromatable,ndthesizeofthetable,<strong>and</strong>iterate(repeataset ofstatementsonceforeachelementofthetable). positionofanelementwithparticularcontents,<strong>and</strong>iterateinorder. Orderedtablesadditionallysupporttheseoperations:insert,remove,or InBoundedBuffer,thesingleactionofthePutserviceconsistsofinsertingthedesignatedlineintotheendofthetableQueue.Theinsert<br />
1.Introductionto<strong>Hermes</strong>29<br />
ifyouwish,bywriting: isordered.However,youmayinsertelementsatanypositioninthetable statementinsertsanelementintotheendofatablebydefaultifthetable<br />
toinsertsomethingatposition3,theremustbeanelementatposition2, anelementpreviouslyatposition3,itmovestoposition4,<strong>and</strong>similarly orelseyouwillgetaRangeErrorexception. allelementsathigherpositionshavetheirpositionsincremented.Ifyoutry youspecifyposition3,thenewelementappearsatposition3.Iftherewas insertElementintoTableat(Position); Inthiscase,youmustsupplyaninteger-valuedposition.Forexample,if<br />
thepositionsofalltheotherelementsmoveupbyone,sotheprevious wewrotetheexpressioncopyof. inGetCM.Line.Whenyouremovetherstelementfromanorderedtable, discardPutCM.Line|inthedenitionofPutLineInterface,parameter intothetable,ratherthancopyingit.Thismeansthatafterthestatement Lineisconstant|wemustmoveacopyofPutCM.Line.Thatexplainswhy isexecuted,thesourceoper<strong>and</strong>isdiscarded.Sincewe'renotallowedto TheGetserviceclauseremovestherstentryfromthetable<strong>and</strong>placesit Onemoretechnicalpointaboutinsert:thestatementmovesitsoper<strong>and</strong><br />
meanssimplythrowingitaway.Callmessages<strong>and</strong>portsaretreatedspecially:Whenacallmessage,oranyvaluewhichcancontaincallmessages<br />
TheQuitservicecallterminatestheloop,<strong>and</strong>henceterminatesthe nalized|thatis,theirvaluesarediscarded.InBoundedBuffer,thatwould bethequeue,thebooleanvariableRunning,thethreeserviceports,<strong>and</strong> secondelementnowbecomesrst. theinitializationport.Formost<strong>Hermes</strong>datatypes,discardingthevalue process. executingitslaststatement.Allvariableswhichremaininitializedare-<br />
discarded,thecallmessagesarereturned.EachcallmessagetypehasadefaultDiscardedexception,e.g.GetLineInterface.Discarded.Whenan<br />
Disconnectedexception.Anyprocesswhichbecomesisolatedbecauseall itsconnectionstotheoutsideworldarebrokenisequivalenttoaterminated inputportisdiscarded,connectionstothatportarebroken;attemptsto (e.g.aninputportwhichmayhaveseveralcallmessagesonitsqueue)is Let'slookmorecloselyatprocesstermination.Aprocessterminatesafter<br />
process<strong>and</strong>canbesafelygarbage-collectedbytheimplementation. sendmessagesoverthoseconnectionswillfail<strong>and</strong>thecallerwillreceivea
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