Hermes: A Tutorial and Reference Manual - Researcher - IBM
Hermes: A Tutorial and Reference Manual - Researcher - IBM
Hermes: A Tutorial and Reference Manual - Researcher - IBM
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Typestatecheckingassignsatypestatetoeachprogrampoint.Atypestate 10 TypestateChecking isamathematicalobjectwhichcanbeinterpretedintwoways:(1)asan assertionthatcertainpropertiesofprogramvariableswillbetruewheneverthatstatementisexecuted;(2)asapointinasemilattice1.Because<br />
by<strong>Hermes</strong>.Wewilldescribethetypestatecheckingalgorithmweuse.We dataowanalysiscanbeused. certainlanguagerulesexpressedintermsofthoseassertionsaresatised. Becausetypestatesformasemilattice,certainwell-knownalgorithmsfrom willtellyouhowtoreadthetablewhichdenestheparticulartypestate rulesforeachoperation. 10.1SyntaxofTypestates Inthissection,wewilldiscusstheparticulartypestatesemilatticeused typestatesareassertions,theycanbeusedtocheckatcompile-timethat<br />
Typestatesareexplicitlywritteninthefollowingsituations:(1)ininterfacedenitions(inputports,callmessages,<strong>and</strong>constraints),(2)intable<strong>and</strong><br />
variantdenitionstoindicatewhattypestateanelementorvariantcomponentmusthave,(3)intheunwrapstatement,toindicatewhattypestate<br />
apolymorphmusthave. enclosedincurlybraces.Anattributeisanattributenamefollowedbya listofvariablenamescalledattributearguments. Atypestateiswrittenasasetofattributesseparatedbycommas<strong>and</strong><br />
dened. Y)Ṫhefollowingattributenamesarebuilt-in:init,case,checked<strong>and</strong> checkeddefinitions.Constraintattributes,likegreaterthan,areuser-<br />
Examplesofattributes:init(X.A),case(V,V.A),greaterthan(X, typestate::=f[attribute[,attribute]...]g<br />
initmusthaveasingleargument,<strong>and</strong>casemusthaveexactlytwoargu- Theargumentsofbuiltinattributesarecheckedasfollows:Attribute attribute::=attribute{nameattribute{arguments<br />
tt1;tt2<strong>and</strong>foranyt0,(t0t1^t0t2))(t0t). ofelementst1<strong>and</strong>t2haveauniquegreatestlowerboundormeettsuchthat 1Asemilatticeisasetwithapartialorderrelationshipsuchthatanypair
Change language