Hermes: A Tutorial and Reference Manual - Researcher - IBM

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types.Additionally,theoperations\and",\or",and\not"aresupported. Booleantypessupportthesameoperationsasunorderedenumeration Thereisapredenedbooleantypecalledpredefined!booleanwhose boolean{association ::=false:named{literal,true:named{literal ::=true:named{literal,false:named{literal 11.HermesOperations103 namedliteralsare'true'and'false'.Youcandeneyourownboolean typeswithdierentliterals.Example: typedenitiondenesanewintegerdomain. bit:boolean(true:'0',false:'1'); Anintegerdomainconsistsofthemathematicalintegers.Eachinteger orangesdomain.Butyoucanconvertbetweentwointegerdomainsusing Example:::=realofaccuracyinteger{literal/integer{literal apples:integer; oranges:integer; Asusual,5intheapplesintegerdomaincan'tbecomparedto5inthe type{construction theconvertoperation. ::=integer numberthatcantinawordofcomputermemory.Incontrast,Hermes usestheusualmathematicaldenitionofinteger.Theresultofaninteger operationisalwayseitherthemathematicallycorrectresult,orelseno discretesubsetofrealnumbersspacedsucientlyclosetogethertomeet asafenumbersuchthattherelativeerror(thedistancebetweenthesafe resultandaDepletionexception. auser-denedaccuracyrequirement.Foreveryrealnumber,thereexists Insomelanguages\integers"aredenedmodulothesizeofthelargest numberandtherealnumberdividedbytherealnumber)islessthanor equaltotheaccuracyrequirement. Arealdomainconsistsofasetofsafenumbers.Safenumbersarea isidenticaltothatshownforintegersabove.Approximaterealarithmetic tegerbetweenthemmusthaveasafeintegerbetweenthem. \preferred"assafenumbers,i.e.anypairofsafenon-integerswithaningrammersaresupported:(1)Zeroisasafenumber,and(2)integersare Theusualrealarithmeticoperationsaresupported;theexpressionsyntax Twootherpropertiesofapproximatearithmeticoftenassumedbypro- velocity:realofaccuracy1/1000000; Theaccuracyisexpressedasafraction,e.g.1/1000000.Example: isperformedasfollows.Theresultiscomputedandasafenumbernearest theexactresultisusedastheresult.Ifthereismorethanonenearestsafe numbertoanumber,anondeterministicselectionismade.
10411.4.ScalarOperations Integer,Real,andNamedLiterals Literalsareexpressionswhichcomputearesultdenedatcompile-time. getatypeerror.Thecompilerwillnotscanthroughthesetofallvisible Examples:23,'blue',"Hello,World!". whetheritisaninteger,real,string,ornamedliteral.Forexamplethe Theyaretreatedasnullaryoperationsforthepurposeoftype-checking. typestoseeifthereisauniqueoneinwhichthisexpressionmakessense. rememberthatifyouwriteanexpressionlike'fair'
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DavidF.BaconArthurP.GoldbergAndyLow
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Preface Thisdocumentcontainsatutori
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iv3TypeandTypestateChecking 5Resear
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Tutorial PartI 1
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ortransactions.AHermesmoduleisastra
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61.2.GettingStarted|ASimpleHermesPr
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81.2.GettingStarted|ASimpleHermesPr
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101.2.GettingStarted|ASimpleHermesP
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121.4.PuttingProcessesTogether thec
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141.4.PuttingProcessesTogether newI
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fullycheckedfortypeandtypestateerro
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constructs:thenewinput-port,connect
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201.5.DeclarationsandDenitions whil
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221.5.DeclarationsandDenitions Stan
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whichtheoutputportconnects|calledth
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261.6.ASimpleServer begin QuitCM:Qu
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281.6.ASimpleServer towritedataabst
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toaservice,whileretainingtheability
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322.1.Requirements PutLine PutLine
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342.3.Interfaces WMInterface:callme
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asmallchangetotheinterfaceFilter.Re
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382.5.Front-endProcess callParms.Ge
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402.5.Front-endProcess paringavalue
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ationtable[expr].Wehaveencounteredt
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ishiddenandinnowayaectsthesemantics
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462.7.TheWindowManager callCurrentW
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name.Ifwewaitedtobuildtheapplicatio
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502.8.CreatingaWindowApplication re
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operandwillnolongerbeinitialized. B
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Followingaretheinferencefunctionsap
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lowestentrycondition(message,port):
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copy(source,destination):Foreachatt
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assert(continued) Description:Evalu
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case(continued) Description:Copythe
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copy(continued) Preconditions: unco
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drop(continued) SpecialRules:Thenum
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exists(continued) SpecialRules:Thes
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forall(continued) Description:Ifeve
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greater(continued) Description:Ifso
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insert{at(table,element,position) T
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integer{literal(result) TypeRules:
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merge{at(continued) Description:Rem
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not(result,source) TypeRules: Appen
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print(variable) TypeRules:None Prec
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emove(element,table) TypeRules: App
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select(continued) SpecialRules:Allt
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subtract(result,source1,source2) Ty
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unary{minus(result,source) TypeRule
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wrap(continued) Preconditions: var(
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definitions predefined:using() Appe
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);'named'->typename:typenameffullg
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{{Specicinformationneededtocomplete
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attrdefinition:record( attributeid:
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statement:record( id:statementid, o
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{{Ablockstatementqualieridentiesthe
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{{expressionisfalse. ifqualifier:re
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{{expression.The'element'rootvariab
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[ASU88]AlfredV.Aho,RaviSethi,andJer
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[SYB87a]RobertE.Strom,ShaulaAlexand
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AppendixC.PredenedModule215 coercio
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AppendixC.PredenedModule217 dening,
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variablename discarded,29 variant,6
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