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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lowestentrycondition(message,port):Thispreconditionappears intotheformaltypestateappearinginip'stypedenitiontoyield therequiredattributes.Allotherattributesinvolvingmessageorits subcomponents. onlyinthesendoperation.Letipbetheinputporttypeassociated withtheportoper<strong>and</strong>,whichisanoutputport.Substitutemessage AppendixB.<strong>Hermes</strong>Operations157<br />
lowestpostcondition(message):Thispreconditionappearsonlywith<br />
polymorphprecondition(oper<strong>and</strong>):Thispreconditionappearsonly maltypestateintoyieldtherequiredattributes.Allotherattributes involvingmessageoritscomponentsareforbidden. tionformessagedeterminesthepreconditions;inthelattercase,the typestateassociatedwiththeexceptionbeingreturneddetermines thepreconditions.Ineithercase,messageissubstitutedintothefor-<br />
thereturn<strong>and</strong>return-exceptionoperations.Intheformercase,<br />
withthewrapoperation.Ifaformaltypestateisspeciedinthe thenormalexittypestateappearinginthecallmessagetypedeni-<br />
assertable():Thispreconditionappearsonlywiththeassertoperation.Iftheconstraintbeingassertedisalreadypresent,thenthis<br />
substitutingoper<strong>and</strong>intotheformaltypestate<strong>and</strong>forbidallother operation,thenthepreconditionrequiretheattributesobtainedby stateisgiven,thispreconditionhasnoeect.2 attributesinvolvingoper<strong>and</strong>oritssubcomponents.Ifnoformaltype-<br />
B.4.2ContextPreconditions variablesotherthantypestate. Thefollowingpreconditionfunctionstestcontext-dependentpropertiesof preconditionhasnoeect.Otherwise,substituteactualarguments forformalparametersinthetypestateappearingwiththeconstraint<br />
var(oper<strong>and</strong>):Thevalueofoper<strong>and</strong>valuemaychangeasaresultof denitiontoyieldtherequiredattributes.Therearenoforbidden<br />
theoperation.Itmustnotbeconstantinthecurrentscope(e.g.via<br />
stateinawrapstatement,sothispreconditionneverhasanyeect. 2Notethatitisimpossible,withthecurrentsyntax,tospecifyaformaltype-<br />
pos(oper<strong>and</strong>):oper<strong>and</strong>mustbetheselectorvariableinan\active" scopeincludesthecurrentoperation,orisassociatedwithaninspect inspectorfor...inspectstatement). theconstantlistinacallmessagedenition,orinthebodyofan selectorinvolvinganorderedtable.Anactiveselectorisonewhose
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