Programming Guide - Actian

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How You Can Communicate Between OpenROAD Applications Using Database EventsDBEventObjectWhen an application receives a database event from the DBMS and places it onthe native event queue, it also initializes a DBEventObject for each frame thatis registered to receive the database event. The attributes of theDBEventObject contain the following information:CurFrame.DBEvent.DBEventNameContains the event's nameCurFrame.DBEvent.DBEventOwnerContains the name of the event's ownerCurFrame.DBEvent.DBEventDatabaseContains the database in which the event is storedCurFrame.DBEvent.DBEventTimeContains the date and time when the event was raisedCurFrame.DBEvent.DBEventTextContains the text specified when the event was raised, if anyIn the frame that receives the event, the values in the DBEventObject are onlyaccessible in the event block that the frame executes for the event. In thisblock, you use the CurFrame variable to reference the event's DBEventObject.How Database Events Work with Multiple SessionsWhen the DBMS receives the event from a sending application, it checks to seewhich applications are registered for that event and sends the event to thoseapplications. Because the DBMS perceives each database session in anapplication as a separate application, a multiple-session application receives adatabase event from the DBMS in the same session in which the registerdbevent statement for that event was issued. The application receives alldatabase events for which it registered in any currently open session even ifthe application is not currently working in the session.When the application receives a database event, OpenROAD ultimatelydispatches it to the frame or frames that are registered to receive that event.When the event reaches the top of the frame's event queue, OpenROADprocesses it. To execute the event block for the event, the frame must beworking at this time in the session in which the event was registered. If theframe is working in a different session when the event reaches the top of theframe's event queue, OpenROAD discards the event.358 <strong>Programming</strong> <strong>Guide</strong>
How You Can Communicate Between OpenROAD Applications Using Database EventsHow You Can Create, Register, and Raise EventsHow You Can Create the EventThe tasks of creating, registering, and raising events are performed with theSQL statements, create dbevent, register dbevent, and raise dbevent,respectively. This section provides a brief overview of each statement as it isused in the OpenROAD programming environment.The SQL create dbevent statement creates a database event. When you createa database event, you are the owner of the event, and it is part of thedatabase with which you were connected when you created the event, forexample:initialize()={create dbevent myevent;commit;}How You Can Register the EventGenerally, you can create database events outside of the applications thatsend or receive them. When you are designing your applications, you candecide what database events are needed and create them all at once.However, it is possible to create and send a database event in the sameapplication.Each frame must be registered to receive those database events that you wantit to receive. To register a frame for a database event, you use the registerdbevent statement. Generally, you place the register dbevent statement in theframe's initialize statement block. However, you can put it in an event block ifyou want, for example:initialize()={register dbevent myevent;commit;}An event registration is associated with a specific session. The frame receivesall events for which it is registered in any currently open session. However, toprocess the event, the frame must be working in the session where the eventwas registered when the event reaches the top of the frame's event queue.Inter-Frame Communication Techniques 359
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Ingres OpenROAD ® 2006Programming
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ContentsChapter 1: Introduction 13I
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Using an Object-oriented Approach t
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How You Can Retrieve Array Informat
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Chapter 12: Managing Event Queues 3
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Chapter 17: Preprocessing Your 4GL
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Chapter 1: IntroductionThis section
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ConventionsConventionsThe following
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Your Support OptionsYour Support Op
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OpenROAD NamesThe rules for these n
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OpenROAD Names3. Enclosing field sc
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OpenROAD NamesThe following code ex
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VariablesThe following illustrates
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VariablesIn the first example, film
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VariablesOpenROAD checks references
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VariablesHow You Can Declare Dynami
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VariablesFor example, assume that y
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ExpressionsHowever, you cannot use
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ExpressionsThe general syntax for h
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ExpressionsCurSessionSpecifies, for
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ExpressionsString OperatorThe conca
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ExpressionsOperatorlikenot likeOper
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Expressions• You can use the esca
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ExpressionsBecause procedures can r
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System-defined FunctionsThis rule h
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System-defined FunctionsNameOperand
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System-defined FunctionsName Operan
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System-defined FunctionsNameshift(c
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System-defined FunctionsSome date f
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System-defined FunctionsThe followi
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System-defined FunctionsCount Funct
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System-defined FunctionsResult Data
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Chapter 3: Writing Scripts and Proc
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ScriptsDeclare local variables that
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ScriptsUserEventSpecifies a user ev
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ScriptsExample—Field and Menu Ite
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ProceduresOpenROAD lets you create
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ProceduresReturning from a Procedur
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ProceduresExample—Local Procedure
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Procedures4GL DataTypedatemoneyfloa
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Calling Procedures• In this call
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Calling ProceduresparameterAssigns
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How Procedure Handles Work (ProcHan
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Compiler LimitationsYou can avoid t
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How You Can Invoke FramesHow the Cu
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How You Can Invoke FramesHow You Ca
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How You Can Invoke FramesFor more i
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How You Can Invoke FramesFor exampl
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How You Can Invoke FramesIf the obj
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How You Can Invoke FramesHow You Ca
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How You Can Invoke Frames• Prompt
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How You Can Invoke FramesThe syntax
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How You Can Run Non-interactive App
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How You Can Reference ObjectsHow Yo
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How You Can Reference ObjectsHow Yo
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How You Can Reference ObjectsUse an
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Using an Object-oriented Approach t
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InheritanceClass RelationshipsYou c
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InheritanceYou can specify a user c
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InheritanceThe Terminate method is
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How You Can Create a User ClassWhen
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How You Can Create a User ClassHow
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How You Can Create a User Class3. G
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How You Can Create a User ClassTo e
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External ClassesHow You Can Use Ext
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External ClassesExample—ActiveX C
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How You Can Manipulate Objects Gene
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Overview of the OpenROAD System Cla
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How You Can Access a Database with
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How You Can Manage TransactionsHow
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How You Can Manage TransactionsDivi
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How You Can Manage TransactionsTo c
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How Programming for Multiple Sessio
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Handling Database ErrorsIn OpenROAD
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Handling Database ErrorsIf a databa
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Handling Database ErrorsFor example
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Handling Database Errorsbeginerr_no
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Arrays and Table Fields—Conceptua
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ArraysBecause an individual attribu
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ArraysDeclaring an array variable d
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ArraysThe following statement puts
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Arraysfor i = custtable.FirstRow to
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ArraysHow You Can Add Rows to an Ar
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ArraysThe inserted row is blank bec
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ArraysThe following code fragment i
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ArraysThese attributes are:AllRowsR
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ArraysAttributes used in a sort can
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ArraysThe format parameter can be a
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Table FieldsTable Fields and Associ
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Table FieldsThe following applicati
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Table FieldsThis syntax references
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Table FieldsFor example, the follow
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Table Field OperationsTable Field C
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Table Field OperationsHow You Can U
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Table Field OperationsWhen you use
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Table Field OperationsBiases can be
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Table Field OperationsThe following
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Table Field OperationsHow You Can T
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Table Field OperationsTableField Me
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Table Field OperationsFor example,
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Table Field OperationsControlling M
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CollectionsCollectionsA collection
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Collections// Open a workbook and p
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Listview_Treeview_DemoImport the De
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Listview FieldsListview FieldsA lis
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Listview FieldsextensionSpecifies a
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Listview FieldsImageIndexSpecifies
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TreeNode and Tree ClassesHeaderClic
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TreeNode and Tree ClassesMaintenanc
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Treeview FieldsHow You Can Build a
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Treeview FieldsThe second window is
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Treeview FieldsThe tree_ex2_class h
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Chapter 9: Working with Images and
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How You Can Work with ImagesThe fol
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How You Can Work with ImagesThe Col
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How You Can Work with ImagesThe Bit
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How You Can Work with Images5. Add
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How You Can Work with Text StringsD
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How You Can Work with Text StringsH
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How You Can Call 3GL ProceduresIn t
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How You Can Use Exec 4GL Statements
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How You Can Link 3GL ProceduresHow
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Page 323 and 324: Event-based ProgrammingField Events
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How You Can Build a Frame Dynamical
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Dynamic Statements ConsiderationsDy
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How You Can Write an AssistantNote:
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How You Can Write an AssistantFirst
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How You Can Write an AssistantBecau
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How You Can Ensure Compatibility Be
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Chapter 17: Preprocessing Your 4GL
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PreprocessorGeneral Preprocessor St
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PreprocessorThe #define StatementTh
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Error ProcessingGuidelines for Usin
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Chapter 18: Debugging Your Applicat
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How You Can Test an ApplicationHow
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How You Can Use Break ConditionsTo
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How You Can Use Break Conditions3.
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How You Can Use Break ConditionsWay
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How You Can Use Break ConditionsSet
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How You Can Use Break Conditions•
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How You Can Use Break ConditionsMet
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How You Can Log Trace InformationDa
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How You Can Monitor a Running Appli
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How You Can Monitor a Running Appli
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How You Can Debug Database QueriesT
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How Debugging an Application WorksS
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How Debugging an Application WorksH
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How Debugging an Application WorksW
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How Debugging an Application WorksH
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How Debugging an Application WorksW
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How Debugging an Application WorksL
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How Debugging an Application WorksA
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Appendix A: SQL Syntax SummaryThis
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SQL Syntax Summarygrant all [privil
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OpenSQL Syntax SummaryOpenSQL Synta
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Operating System CommandsThe follow
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BitmapObject classThe BitmapObject
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external classAn external class def
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local variableLocal variables conta
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StringObject classThe StringObject
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Index'' ' (single quotation marks)c
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Attributesdefined • 28referencing
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using to copy data • 244using wit
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application threads • 444array di
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examining values • 473hexadecimal
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Gmoney • 51numeric list • 53pad
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Namesapplication • 21dynamic •
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ReadOps attributesettings • 243Re
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concat function • 54functions •
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event chains • 323event queue •
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