Hermes: A Tutorial and Reference Manual - Researcher - IBM

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thetableisordered,theelementisinsertedattheendofthetable.Ifthe tableiskeyed,theDuplicateKeyexceptionisraisediftheinsertionwould operationisillegal.Ifithasahighertypestate,thetypestateislowered.If Thevaluemusthavetheelementtypestate.Ifithasalowertypestate,the fromasourcevariable.Thesourcevariablemustbeoftheelementtype. Theinsertstatementaddsanewelementtoatablebymovinginavalue 11.HermesOperations111 actlylikeinsert,exceptithasanadditionaloperandoftypepredefined!integer haveviolatedtherequirementofuniquekeys. whichspecieswheretoinserttheelement.Ifthispositionisnegative,or greaterthanthenumberofelementsinthetable,theexceptionRangeError takesprecedence. mayberaisedexactlyasforinsert,exceptthataRangeErrorexception israised.Otherwise,theelementisinsertedatthedesignatedposition.The positionsofearlierelementsinthetableremainthesame.Thepositionsof laterelements(ifany)areincreasedbyone.TheexceptionDuplicateKey Theinsert-atstatementislegalonlyfororderedtables.Itbehavesex- sinceitsvalueismovedandnotcopied. Remove Aftereitherinsertorinsert-at,theelementvariableisuninitialized, noselectedelement,theexceptionNotFoundisraised.Thepreviousvalue, removedfromthetableandmovedintothedestinationvariable.Ifthereis Theremovestatementhastwooperands:adestinationelement,whichappearsafterthewordremove,andaselector.Thechosenselectedelementis Examples: simple{statement ifany,ofthedestinationvariableisdiscarded. removeCharfromString[0]; ::=removeelement{variablefromselector one.Ifthereisnone,anexceptionisraised.Thesecondstatementremoves thesmallestintegerfromIntbag|theintegerIsuchthatallintegersin empty. Extract IntbagareatleastaslargeasI.Itwillraiseanexceptionifthetableis removeMinfromIinIntBag Therststatementremovestherstcharacterfromthestring,ifthereis where(forallofJinIntbagwhere(J>=I)); appearsafterthewordextract,andaselector.Allchosenselectedele- Theextractstatementhastwooperands:adestinationtable,which simple{statement ::=extracttable{variablefromselector
isdiscarded. Merge,Merge-At 11211.6.TableOperations mentsareremovedfromthetablenamedintheselector,andmovedinto thedestinationtable.Ifnoelementsareselected,thedestinationtableis initializedtoanemptytable.Thepreviousvalue,ifany,ofthedestination thesourcevariablewillbeuninitialized.Ifthetableisordered,theelements(ifany)fromthesourcetablewillbeinsertedattheendofthe elementswillbeofthesametypeandtypestate.Onnormalcompletion, tinationtable.Thetwotablesareofthesametype|meaningthatthe Themergestatementmovesthecontentsofthesourcetableintothedes- simple{statement destinationtable,andtheirorderwillbepreserved.Ifthetableiskeyed, ::=mergetable{expressionintotable{variable theDuplicateKeyexceptionisraisedifthemergewouldhaveviolatedthe [atposition{expression] requirementofuniquekeys. asformerge,exceptthataRangeErrorexceptiontakesprecedence. whichspecieswheretoinsertthesourcetableelements.Ifthisposition actlylikemerge,exceptithasanadditionaloperandoftypepredefined!integer ceptionRangeErrorisraised.Otherwisetheelementsareinsertedatthe designatedposition.Thepositionsofearlierelementsinthetableremain thesame.Thepositionsoflaterelements(ifany)areincreasedbythenumberofelementsmerged.TheexceptionDuplicateKeycanberaisedexactly isnegative,orgreaterthanthenumberofelementsinthetable,theex- Themerge-atstatementislegalonlyfororderedtables.Itbehavesex- table.Thiscopyisstoredintoanewvariable{theinspectvariablehaving Inspect-table Thisstatementmakesaconstantcopyofthechosenselectedelementofa thesamenameastheelementvariableoftheselector.Theinspectvariable isautomaticallydeclaredtobeoftheelementtypeofthetable,andtohave compound{statement ascopeincludingtheclausewithinthebodyoftheinspectstatement.If ::=inspectselectorbegin thereisnoselectedelement,theNotFoundexceptionisraised. endinspect [statement;]... be\dangerous"(receive,return)whenperformedonordinarycopiesare aconstantcopyofanyvalue.Thisisbecausetheoperationswhichwould sages,inputports,orvaluescontainingthem),itisalwayslegaltomake Whereasitisillegaltomakeordinarycopiesofcertainvalues(callmes-
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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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522.8.CreatingaWindowApplication be
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examplesillustratedhere. errorhandl
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563.TypeandTypestateChecking anerro
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583.TypeandTypestateChecking Therei
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Page 78 and 79: 6Introduction Thereferencemanualpre
Page 80 and 81: 7LexicalandSyntacticRules lectionso
Page 82 and 83: 8Resolution name,attributename,exce
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Page 100 and 101: 11 HermesOperations Throughoutthere
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Page 142 and 143: A.1LexicalRules Webeginwiththerules
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Page 156 and 157: Typestatesappearinginparticularcont
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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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