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  • iphone - how to properly handle exceptional situations (signals ?)

    - by pmilosev
    Hi In my iphone app, I want to provide some sort of app termination handler that will do some final work (delete some sensitive data) before the application terminates. I want to handle as much of the termination situations as possible: 1) User terminates the app 2) The device runs out of battery 3) The system terminates the app due to some reason (e.g. out of memory or app freeze) 4) Application crashes (EXC_BAD_ACCESS or SIGSEGV) Any other exceptional situation ? What is the best way to achieve this (e.g. is applicationWillTerminate method called in situation 2) ? Is it possible to do the cleanup in a signal handler (includes iPhone Security framework calls) ? regards

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  • Handling Complex Rules in in GUI applciations (C++ or C#)

    - by Canacourse
    Im working on a dialog box in which several rules must be satisfied before the OK button is enabled. Currently any action on the page such as entering data or selecting an item from a drop down list (amongst other things) calls a single function called ProcessEvent() - this function handles all logic and either enables or disables the OK button. My problem is I finding it difficult making the rules concise and understandable. Some of the rules can be negated by another action on the dialog and I have now ended up with if else statements all over the place or which are difficult to read and follow & extend. The code below is a simplification of the problem but demonstrates it well. How do I handle this problem better (If its Possible) bool CWorkstation::ProcessEvent(void) { UpdateData(); CharCount = GetDlgItemInt(IDC_CharCount, NULL, FALSE); //get latest if ( IsDlgButtonChecked(IDC_USEDBNAME)) { if (!IsDlgButtonChecked(IDC_MAXDBNAME)) { EnableNext(TRUE); } } if (IsDlgButtonChecked(IDC_MAXDBNAME) && CharCount) { if (IsDlgButtonChecked(IDC_USEXMLNAME)) { if ( PrefixName.IsEmpty() ) { EnableNext(FALSE); } else { EnableNext(TRUE); } } } if (IsDlgButtonChecked(IDC_USEXMLNAME) && PrefixName.GetLength() > 1) { EnableNext(TRUE); } if ( IsDlgButtonChecked(IDC_WSAUTONAME) || IsDlgButtonChecked(IDC_RENAMEIFDUP)) { // TRACE("IDC_WSAUTONAME is Checked\n"); if ( IsDlgButtonChecked(IDC_USEXMLNAME) && PrefixName.GetLength() > 1 ) { if ( IsDlgButtonChecked(IDC_IDC_USESHORTNAME) ) { EnableNext(TRUE); } else if ( IsDlgButtonChecked(IDC_USELONGNAME) ) { EnableNext(TRUE); } else { EnableNext(FALSE); } } if ( !IsDlgButtonChecked(IDC_USEPREFIX) ) { if ( IsDlgButtonChecked(IDC_IDC_USESHORTNAME) || IsDlgButtonChecked(IDC_USELONGNAME) ) { EnableNext(TRUE); } } return false; } }

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  • Which .NET exception to throw for invalid database state?

    - by jslatts
    I am writing some data access code and I want to check for potentially "invalid" data states in the database. For instance, I am returning a widget out of the database and I only expect one. If I get two, I want to throw an exception. Even though referential integrity should prevent this from occurring, I do not want to depend on the DBAs never changing the schema. I would like to use the System.IO.InvalidDataException, except that I am not dealing with a file stream so it would be misleading. I ended up going with a generic applicationexception. Anyone have a better idea?

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  • Handling a Long Running jsp request on the server using Ajax and threads

    - by John Blue
    I am trying to implement a solution for a long running process on the server where it is taking about 10 min to process a pdf generation request. The browser bored/timesout at the 5 mins. I was thinking to deal with this using a Ajax and threads. I am using regular javascript for ajax. But I am stuck with it. I have reached till the point where it sends the request to the servlet and the servlet starts the thread.Please see the below code public class HelloServlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("POST request!!"); LongProcess longProcess = new LongProcess(); longProcess.setDaemon(true); longProcess.start(); request.getSession().setAttribute("longProcess", longProcess); request.getRequestDispatcher("index.jsp").forward(request, response); } } class LongProcess extends Thread { public void run() { System.out.println("Thread Started!!"); while (progress < 10) { try { sleep(2000); } catch (InterruptedException ignore) {} progress++; } } } Here is my AJax call <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html><head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>My Title</title> <script language="JavaScript" > function getXMLObject() //XML OBJECT { var xmlHttp = false; xmlHttp = new XMLHttpRequest(); //For Mozilla, Opera Browsers return xmlHttp; // Mandatory Statement returning the ajax object created } var xmlhttp = new getXMLObject(); //xmlhttp holds the ajax object function ajaxFunction() { xmlhttp.open("GET","HelloServlet" ,true); xmlhttp.onreadystatechange = handleServerResponse; xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded'); xmlhttp.send(null); } function handleServerResponse() { if (xmlhttp.readyState == 4) { if(xmlhttp.status == 200) { document.forms[0].myDiv.value = xmlhttp.responseText; setTimeout(ajaxFunction(), 2000); } else { alert("Error during AJAX call. Please try again"); } } } function openPDF() { document.forms[0].method = "POST"; document.forms[0].action = "HelloServlet"; document.forms[0].submit(); } function stopAjax(){ clearInterval(intervalID); } </script> </head> <body><form name="myForm"> <table><tr><td> <INPUT TYPE="BUTTON" NAME="Download" VALUE="Download Queue ( PDF )" onclick="openPDF();"> </td></tr> <tr><td> Current status: <div id="myDiv"></div>% </td></tr></table> </form></body></html> But I dont know how to proceed further like how will the thread communicate the browser that the process has complete and how should the ajax call me made and check the status of the request. Please let me know if I am missing some pieces. Any suggestion if helpful.

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  • Centralizing Messagebox handling for application

    - by DRapp
    I'm wondering how others deal with trying to centralize MessageBox function calling. Instead of having long text embedded all over the place in code, in the past (non .net language), I would put system and application base "messagebox" type of messages into a database file which would be "burned" into the executable, much like a resource file in .Net. When a prompting condition would arise, I would just do call something like MBAnswer = MyApplication.CallMsgBox( IDUserCantDoThat ) then check the MBAnswer upon return, such as a yes/no/cancel or whatever. In the database table, I would have things like what the messagebox title would be, the buttons that would be shown, the actual message, a special flag that automatically tacked on a subsequent standard comment like "Please contact help desk if this happens.". The function would call the messagebox with all applicable settings and just return back the answer. The big benefits of this was, one location to have all the "context" of messages, and via constants, easier to read what message was going to be presented to the user. Does anyone have a similar system in .Net to do a similar approach, or is this just a bad idea in the .Net environment.

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  • What to log when an exception occurs?

    - by Rune
    public void EatDinner(string appetizer, string mainCourse, string dessert) { try { // Code } catch (Exception ex) { Logger.Log("Error in EatDinner", ex); return; } } When an exception occurs in a specific method, what should I be logging? I see a lot of the above in the code I work with. In these cases, I always have to talk to the person who experienced the error to find out what they were doing, step through the code, and try to reproduce the error. Is there any best practices or ways I can minimize all this extra work? Should I log the parameters in each method like this? Logger.Log("Params: " + appetizer + "," + mainCourse + "," + dessert, ex); Is there a better way to log the current environment? If I do it this way, will I need to write out all this stuff for each method I have in my application? Are there any best practices concerning scenarios like this?

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  • Set reference = null in finally block?

    - by deamon
    A colleague of mine sets reference to null in finally blocks. I think this is nonsense. public Something getSomething() { JDBCConnection jdbc=null; try { jdbc=JDBCManager.getConnection(JDBCTypes.MYSQL); } finally { JDBCManager.free(jdbc); jdbc=null; // <-- Useful or not? } } What do you think of it?

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  • Is it possible to call the main(String[] args) after catching an exception?

    - by Jason
    I'm working on a Serpinski triangle program that asks the user for the levels of triangles to draw. In the interests of idiot-proofing my program, I put this in: Scanner input= new Scanner(System.in); System.out.println(msg); try { level= input.nextInt(); } catch (Exception e) { System.out.print(warning); //restart main method } Is it possible, if the user punches in a letter or symbol, to restart the main method after the exception has been caught?

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  • Handling Denormalized Schema with Eclipselink

    - by iamrohitbanga
    Hello All I have a denormalized table containing employee information. The fields are employee id, name and department name. The primary key is a composite one consisting of all three fields. An employee can belong to multiple departments. I want to read/write the objects in the table using the Eclipselink Dynamic Persistence API (which is infact a wrapper on top of JPA descriptors etc.). Example Data: 1 e1 dep1 2 e1 dep2 3 e2 dep1 4 e2 dep3 5 e3 dep1 5 e3 dep2 5 e3 dep3 A normal ReadAllQuery (select query) on the table returns a DynamicEntity corresponding to each row in the table. However I want to club all entities based on the emp id and return all the departments he belongs to as a list. I can merge the entities after retrieving them but if I can use some Eclipselink feature out of the box then it would be better. One way to do the read is the following: I create two dynamic types corresponding to employee: Having id,name as the primary key Having id, department as the primary key, I create a OneToManyMapping from the first type to the second one. Then when I query the first type it does return the departments to which employee belongs as a list of DynamicEntity of the second type. This satisfies the read scenario. Is there a better way of doing this? Is this inherently supported by Eclipselink or JPA? I cannot get the same dynamic type configuration working for the write scenario. This is because when I write the changes using the writeObject method of UnitOfWork, it generates insert queries which enter the following entries in the table id name department 102 emp_102 102 st 102 dep_102 102 dep_102 102 dep_102 instead of: id name department 102 emp_102 st 102 emp_102 dep_102 102 emp_102 dep_102 102 emp_102 dep_102 Is there any way I can get write to work with this schema using eclipselink? I want to avoid doing the heavy lifting of merging the rows for such a denormalized schema or generating each row before doing a write. Is there no clean way of doing this using Eclipselink or JPA? Thanks in Advance.

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  • Global Exception Handlers in Java

    - by Samuh
    I am thinking of setting up a global, default Exception handler for my (Android) Mobile application(which uses Java syntax) using Thread.setDefaultUncaughtExceptionHandler(...) call. I am thinking of just displaying an Alert Dialog with appropriate message to the user. Are there any gotchas, caveats and rules that one needs to follow when setting DefaultExceptionHandlers? Any best practices like making sure that the process is killed, full stack trace is written to logs etc. ? Links to documentation, tutorials etc. that can throw some light on this are welcome. Thanks.

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  • try .. catch blocks - when to use

    - by Konrad
    I have always been of the belief that if a method can throw an exception then it is reckless not to protect this call with a meaningful try block. I just posted 'You should ALWAYS wrap calls that can throw in try, catch blocks.' to this question and was told that it was 'remarkably bad advice' - I'd like to understand why. Thanks!

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  • Mapping the System.Exception with FaultException

    - by user357342
    I have used exception sheilding feature of application block, to map System.Exception with class that is marked as DataContract. It works very well. But When I have mapped the System.Exception with FaultException, I got the below error message. "An error has occurred while consuming this service. Please contact your administrator for more information. Error ID: fe2d28b5-8d26-430e-baf4-fe4b39da853c" Please let me know whether I can map the System.Exception with FaultException

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  • Common Utility for Exception Searching

    - by Andrew
    I wrote this little helper method to search the exception chain for a particular exception (either equals or super class). However, this seems like a solution to a common problem, so was thinking it must already exist somewhere, possibly in a library I have already imported. So, any ideas on if/where this might exist? boolean exceptionSearch(Exception base, Class<?> search) { Throwable e = base; do { if (search.isAssignableFrom(e.getClass())) { return true; } } while ((e = e.getCause()) != null); return false; }

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  • Basic Python: Exception raising and local variable scope / binding

    - by SuperJdynamite
    I have a basic "best practices" Python question. I see that there are already StackOverflow answers tangentially related to this question but they're mired in complicated examples or involve multiple factors. Given this code: #!/usr/bin/python def test_function(): try: a = str(5) raise b = str(6) except: print b test_function() what is the best way to avoid the inevitable "UnboundLocalError: local variable 'b' referenced before assignment" that I'm going to get in the exception handler? Does python have an elegant way to handle this? If not, what about an inelegant way? In a complicated function I'd prefer to avoid testing the existence of every local variable before I, for example, printed debug information about them.

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  • Freetype2 (error-)return value documentation

    - by Awaki
    In short, I'm looking for documentation that would limit the error situations to check for after a Freetype library function failed, much like the OpenGL and Win32 APIs document the error codes generated by their respective functions. I can't seem to find such documentation though, so I was wondering how to best handle translation of Freetype errors to typed exceptions. Background: I am currently in the process of implementing font-rendering capability (using Freetype) for my GUI framework, which makes strong use of typed exceptions to indicate error situations. However, the Freetype docs seem to completely omit what errors can be expected from what functions. That, if such documentation does indeed not exist, would basically leave me with two options: either guessing which errors make sense for a certain Freetype function (obviously prone to mistakes on my part), or considering every error code for translation into appropriate exceptions (less verbose since I would have to write the translation only once). Performance isn't really critical in the code that calls the Freetype library, so even the latter option would probably be acceptable, but surely there must be some kind of documentation on which library calls may return what Freetype error? Is there any such documentation which I just somehow managed to not find? Should I go the route of generically expecting every error code for translation? Or are there other ways to approach this problem? By the way, I wanted to avoid introducing some kind of generic FreetypeException (containing a description of the Freetype error) since I intended to completely hide what libraries I'm using (not from a legal point-of-view, mind you), but I guess I can be convinced to do this anyway if the consensus is that it would be the best option. I don't think it matters for this question, but I'm writing in C++.

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  • In Asp.net i'm not able to catch any exception properly?

    - by Anand
    In Asp.net (c#),i'm not able to catch exception(FileNotFoundException) properly... i don't know the reason..Actually File s not there..But catch statement fails to catch the exception.. here is the code.. try { System.Drawing.Image imgg1 = System.Drawing.Image.FromFile(Server.MapPath("").ToString() + "\\images\\img1.jpg"); } catch (FileNotFoundException) { Response.Write("<script>alert('Please Select and upload Student's Photo');</script>"); }

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  • Session handling in python / django

    - by Gaurav
    I am creating an application that lets users login using Google, Facebook and the website's native login. The site is being built in Python / Django. What would be the best way to handle login, session management and user authentication? I do not want to use the in-built Django user management. I am using Django very sparingly(URLs, templates)

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  • How to solve Only Web services with a [ScriptService] attribute on the class definition can be called from script

    - by NevenHuynh
    I attempt to use webservice return POCO class generated from entity data model as JSON when using Jquery AJAX call method in webservice. but I have problem with error "Only Web services with a [ScriptService] attribute on the class definition can be called from script", and getting stuck in it, Here is my code : namespace CarCareCenter.Web.Admin.Services { /// <summary> /// Summary description for About /// </summary> [WebService(Namespace = "http://tempuri.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] [System.ComponentModel.ToolboxItem(false)] // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. // [System.Web.Script.Services.ScriptService] public class About : System.Web.Services.WebService { [ScriptMethod(ResponseFormat = ResponseFormat.Json)] [WebMethod] public static Entities.Category getAbout() { Entities.Category about = new Entities.Category(); using (var context = new CarCareCenterDataEntities()) { about = (from c in context.Categories where c.Type == "About" select c).SingleOrDefault(); } return about; } } } aspx page : <script type="text/javascript"> $(document).ready(function () { $.ajax({ type: 'POST', dataType: 'json', contentType: 'application/json; charset=utf-8', url: '/Services/About.asmx/getAbout', data: '{}', success: function (response) { var aboutContent = response.d; alert(aboutContent); $('#title-en').val(aboutContent.Name); $('#title-vn').val(aboutContent.NameVn); $('#content-en').val(aboutContent.Description); $('#content-vn').val(aboutContent.DescriptionVn); $('#id').val(aboutContent.CategoryId); }, failure: function (message) { alert(message); }, error: function (result) { alert(result); } }); $('#SaveChange').bind('click', function () { updateAbout(); return false; }); $('#Reset').bind('click', function () { getAbout(); return false; }) }); function updateAbout() { var abt = { "CategoryId": $('#id').val(), "Name": $('#title-en').val(), "NameVn": $('#title-vn').val(), "Description": $('#content-en').val(), "DescriptionVn": $('#content-vn').val() }; $.ajax({ type: "POST", url: "AboutManagement.aspx/updateAbout", data: JSON.stringify(abt), contentType: "application/json; charset=utf-8", dataType: "json", success: function (response) { var aboutContent = response.d; $('#title-en').val(aboutContent.Name); $('#title-vn').val(aboutContent.NameVn); $('#content-en').val(aboutContent.Description); $('#content-vn').val(aboutContent.DescriptionVn); }, failure: function (message) { alert(message); }, error: function (result) { alert(result); } }); } </script> Do any approaches to solve it ? Please help me . Thanks

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  • error handling with .post()

    - by meo
    I have to modify a project written by someone else. Because the code is a mess i can't really change this $.post() (or replace it by $.ajax()). What i need to do, is to know if the post returns something else then json and return it. $.post('balbal.html', json, function(data) { ... my coude ... }, 'json') I can see the post response i the console.log. Is there a simple way to retrieve it?

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  • Handling static files with Django / lighttpd

    - by ptikobj
    I know that there is already a question (actually some more) about this, but the answers to them didn't help me out very much, as I am pretty new to lighttpd. I have one folder which contains .pdf-files. When doing a HttpResponseRedirect to the locations of one of those .pdf-files, the user should be able to download the .pdf file (or view it in the browser). Right now, Django just redirects to my "home" html page, without showing any pdf-file. Somehow, I will have to tell lighttpd that Django shouldn't handle this directory anymore. Is this the only thing I need to do? If yes, how should i do it?

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  • How do I propagate an exception thrown by croak in forked child to parent/foreground process?

    - by Pedro Silva
    Throwing an exception via croak in a forked child process seems to print the error as a background process would. That is, it clobbers the shell prompt. If I die instead of croak, the the error message pops up as a foreground process. I've trying to find out why that is in the Carp documentation without any luck. Here's what I mean. The croak version: $ perl Wrapper.pm $ error: ... does not exist at Wrapper.pm line 624 The die version: $ perl Wrapper.pm error: ... does not exist at Wrapper.pm line 515. I tried trapping the fork and printing $@ to STDERR and exiting, but that didn't have an effect. Any ideas? I'd like to be able to use croak in this particular case.

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  • .net exception pool

    - by javier
    I want to create a mecanism in a large .net application to handle all the exceptions in the application, and to save the error messages (in db or log file) so these errors can be fixed, and so we are aware of the problems in the application. Does anyone know a good way of creating a library to handle and process all the exceptions?. Are there any tools around that can simplify my task. What aproach would you suggest me to take.... If you previously implemented something similar to what I want to do, I do want to heard from you Thanks all

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  • Exceptions over remote methods

    - by Andrei Vajna II
    What are the best practices for exceptions over remote methods? I'm sure that you need to handle all exceptions at the level of a remote method implementation, because you need to log it on the server side. But what should you do afterwards? Should you wrap the exception in a RemoteException (java) and throw it to the client? This would mean that the client would have to import all exceptions that could be thrown. Would it be better to throw a new custom exception with fewer details? Because the client won't need to know all the details of what went wrong. What should you log on the client? I've even heard of using return codes(for efficiency maybe?) to tell the caller about what happened. The important thing to keep in mind, is that the client must be informed of what went wrong. A generic answer of "Something failed" or no notification at all is unacceptable. And what about runtime (unchecked) exceptions?

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  • Why does "return ERROR" only work with exceptions?

    - by ThreaT
    In the struts.xml I use: <result name="error">error</result> Then in my action I use: addActionError("ERROR RETURNED"); return ERROR; When I submit the form then it just goes to a blank page and does nothing. However, if I FORCE an exception to be thrown in the action then it goes to the error page and shows the ActionError message. So am I doing this wrong? If so, how should I tell struts to show an error page using "if statements" instead of relying solely on expensive try catches? EDIT 1: I'm using struts 2 version: 2.1.8.1 EDIT 2: For example, here is my action code that I'm using to test: String test = ""; int number = 0; try { if (number == 1) { System.out.println("number 1: " + number); test = SUCCESS; } else if (number == 2) { System.out.println("number 2: " + number); addActionError("ERROR RETURNED?"); addActionMessage("TESTTEST"); test = ERROR; } else if (number == 3) { System.out.println("number 3: " + number); addActionError("ERROR RETURNED?"); addActionMessage("TESTTEST"); test = INPUT; } else { System.out.println("number 4: " + number); test = LOGIN; } } catch (Exception e) { addActionError("ERROR RETURNED? " + e); } return test; And here is my JSP code: <s:form action="number_save" method="post"> <s:textfield name="number" label="Enter number" /> </s:form> <s:actionerror /> <s:fielderror /> <s:actionmessage /> EDIT 3: Here is a longer version of my struts.xml: <action name="number" method="numberCreate" class="NumberActionBean"> <result>number.jsp</result> </action> <action name="error"> <result>error.jsp</result> </action> <action name="number_save" method="numberSave" class="NumberActionBean"> <interceptor-ref name="defaultStack"></interceptor-ref> <result name="success" type="redirect">index</result> <result name="input" type="redirect">number</result> <result name="error">error</result> <result name="login" type="redirect">login</result> <result name="none">number</result> </action> EDIT 4: My error.jsp is simply a <s:actionerror /> tag with the general taglibs and html tags...

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  • C# Dynamic Keyword exception handling

    - by user972255
    The below code throws an exception when executing this line (i.e. something.Add(name)). I want to catch the actual exception when executing this. I mean I don't want to use catch(Exception ex) instead of that I want to know what is the correct exception thrown here. try { dynamic name= "test"; var something = new List<decimal>(); something.Add(name); } catch(Exception ex) { throw ex; } Thanks in advance.

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