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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9611.2.TheDepletionException 11.3ControlFlowOperations Block compound{statement<br />
constant{section ::=block endblock [h<strong>and</strong>ler]... begin [declaration{section] [constant{section]<br />
declaration{section ::=constant([base{variable[,base{variable]...]) ::=declare[declaration;]... [statement;]...<br />
declarenewvariables,youcanspecifythatthevaluesofexistingvariables Ablockstatementintroducesanewscope.Withinthisscope,youcan h<strong>and</strong>ler::=on([exception{name[,exception{name]...]) ::=onexit([exit{name[,exit{name]...])<br />
bythenamesoftheexitsorexceptionsith<strong>and</strong>les.Theabbreviationothers Theotherclausesaretheh<strong>and</strong>lerclauses.Eachh<strong>and</strong>lerclauseispreceded mustremainconstant,<strong>and</strong>youcanprovideh<strong>and</strong>lersforexceptionsorexits withinthemainbodyoftheblock. Thestatementseriesafterthewordbeginisthemainclauseoftheblock. [statement;]...<br />
withinah<strong>and</strong>lerclausecannotcausecontroltotransfertoanotherh<strong>and</strong>ler clauseofthesameblock. totheh<strong>and</strong>leroftheinnermostblock.Rememberthatexceptionsraised Twoclausesofthesameblockcannoth<strong>and</strong>lethesameexitorexception. containingh<strong>and</strong>lersforthesameexceptionorexit,controlwilltransfer st<strong>and</strong>sforallexceptionswhicharenotexplicitlyh<strong>and</strong>led.Restriction:<br />
issuinganexitstatement,thentheclauseissaidtoexitnormally..Ifany Ifastatementiswithinthemainclausesoftwoormorenestedblocks controltotransfertotheclauseheadedbythatexceptionorexitname. Ifallstatementsofaclausecompletewithoutraisinganexceptionor Anexceptionorexitraisedwithinthemainclauseofablockcauses<br />
wordsblock<strong>and</strong>endblockdonotappear.Asecondblockwithanempty clauseofablockexitsnormally,thentheblockitselfexitsnormally. on(others)h<strong>and</strong>lerisimpliedaroundthisblock.Thisisnecessarysothat Thebodyofaprocessstatementisactuallyablock,althoughthe
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