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  • Correct Exceptions in C++

    - by Dr.Ackula
    I am just learning how to handle errors in my C++ code. I wrote this example that looks for a text file called some file, and if its not found will throw an exception. #include <iostream> #include <fstream> using namespace std; int main() { int array[90]; try { ifstream file; file.open("somefile.txt"); if(!file.good()) throw 56; } catch(int e) { cout<<"Error number "<<e<<endl; } return 0; } Now I have two questions. First I would like to know if I am using Exceptions correctly. Second, (assuming the first is true) what is the benefit to using them vs an If else statement?

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  • Handling primary key duplicates in a data warehouse load

    - by Meff
    I'm currently building an ETL system to load a data warehouse from a transactional system. The grain of my fact table is the transaction level. In order to ensure I don't load duplicate rows I've put a primary key on the fact table, which is the transaction ID. I've encountered a problem with transactions being reversed - In the transactional database this is done via a status, which I pick up and I can work out if the transaction is being done, or rolled back so I can load a reversal row in the warehouse. However, the reversal row will have the same transaction ID and so I get a primary key violation. I've solved this for now by negating the primary key, so transaction ID 1 would be a payment, and transaction ID -1 (In the warehouse only) would be the reversal. I have considered an alternative of generating a BIT column, where 0 is normal and 1 is reversal, then making the PK the transaction ID and the BIT column. My question is, is this a good practice, and has anyone else encountered anything like this? For reference, this is a payment processing system, so values will not be modified, so there will only ever be transactions and reversals.

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  • Strange exception phenomenon in Windows 7

    - by Level 2
    I spot some interesting articles about exception handle in CodeProject http://www.codeproject.com/KB/cpp/seexception.aspx After reading, I decided to do some experiment. The first time I try to execute the following code char *p; p[0] = 0; The program died without question. But After several times when I executed the same problem binary code, it magically did fine. Even the following code is doing well. Any clue or explanation? char *p p[1000] = 'd'; cout<<p[1000]<<endl; My O/S is Windows 7 64bit and compiler is VS2008 rc1.

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  • 'Advanced' Console Application

    - by keynesiancross
    Hi all, I'm not sure if this question has been answered elsewhere and I can't seem to find anything through google that isn't a "Hello World" example... I'm coding in C# .NET 4.0. I'm trying to develop a console application that will open, display text, and then wait for the user to input commands, where the commands will run particular business logic. For example: If the user opens the application and types "help", I want to display a number of statements etc etc. I'm not sure how to code the 'event handler' for user input though. Hopefully this makes sense. Any help would be much appreciated! Cheers.

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  • [c++] accessing the hidden 'this' pointer

    - by Kyle
    I have a GUI architecture wherein elements fire events like so: guiManager->fireEvent(BUTTON_CLICKED, this); Every single event fired passes 'this' as the caller of the event. There is never a time I dont want to pass 'this', and further, no pointer except for 'this' should ever be passed. This brings me to a problem: How can I assert that fireEvent is never given a pointer other than 'this', and how can I simplify (and homogenize) calls to fireEvent to just: guiManager->fireEvent(BUTTON_CLICKED); At this point, I'm reminded of a fairly common compiler error when you write something like this: class A { public: void foo() {} }; class B { void oops() { const A* a = new A; a->foo(); } }; int main() { return 0; } Compiling this will give you ../src/sandbox.cpp: In member function ‘void B::oops()’: ../src/sandbox.cpp:7: error: passing ‘const A’ as ‘this’ argument of ‘void A::foo()’ discards qualifiers because member functions pass 'this' as a hidden parameter. "Aha!" I say. This (no pun intended) is exactly what I want. If I could somehow access the hidden 'this' pointer, it would solve both issues I mentioned earlier. The problem is, as far as I know you can't (can you?) and if you could, there would be outcries of "but it would break encapsulation!" Except I'm already passing 'this' every time, so what more could it break. So, is there a way to access the hidden 'this', and if not are there any idioms or alternative approaches that are more elegant than passing 'this' every time?

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  • Best practices for handling binary data in Ruby?

    - by StackedCrooked
    What are the best practices for reading and writing binary data in Ruby? In the code sample below I needed to send a binary file using over HTTP (as POST data): f = File.new("resp.der", "r") # binary file begin while true out.syswrite(f.sysread(1)) # out is an output stream (type IO) end rescue EOFError => err puts "Sent response." end While this code seems to do a good job, it probably isn't very idiomatic. How can I improve it?

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  • What is a good "Error Checking" Pattern (Java)?

    - by Jack
    I'll explain what I mean by input error checking. Say you have a function doSomething(x). If the function completes successfully doSomething does something and returns nothing. However, if there are errors I'd like to be notified. That is what I mean by error checking. I'm looking for, in general, the best way to check for errors. I've thought of the following solutions, each with a potential problem. Flag error checking. If doSomething(x) completes successfully return null. Otherwise, it returns a boolean or an error string. Problem: Side effects. Throwing an exception. Throw an exception if doSomething(x) encounters an error. Problem: If you are performing error checking for parameters only, throwing an IllegalArgumentExceptionseems inappropriate. Validating input prior to function call. If the error checking is only meant for the parameters of the function, then you can call a validator function before calling the doSomething(x) function. Problem: What if a client of the class forgets to call the validator function before calling doSomething(x)? I often encounter this problem and any help or a point in the right direction would be much appreciated.

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  • Neural Network: Handling unavailable inputs

    - by Mike
    Hopefully the last NN question you'll get from me this weekend, but here goes :) Is there a way to handle an input that you "don't always know"... so it doesn't affect the weightings somehow? Soo... if I ask someone if they are male or female and they would not like to answer, is there a way to disregard this input? Perhaps by placing it squarely in the centre? (assuming 1,0 inputs at 0.5?) Thanks

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  • null reference exception was unhandled by user code

    - by user238319
    sir, i develop the following code in vs2005, now i just using this module in my new project @ vs 2008.. But this error was araised. I cant able to fix this problem... Private Sub DataAccess() Dim errHandle As New ErrorHandler Dim lobjCommon As New eCopsCommonFunctions Try AccessCodeDrplst.DataSource = CType(lobjCommon.gfuncGetAllEnrollmentSource(), DataSet) AccessCodeDrplst.DataValueField = "DataAccessCode" AccessCodeDrplst.DataTextField = "DataAccessDesc" AccessCodeDrplst.DataBind() 'lstEnrollmentSourceCode.DataValueField = "EnrollmentSourceCode" 'lstEnrollmentSourceCode.DataTextField = "EnrollmentSourceDesc" 'lstEnrollmentSourceCode.DataBind() '"Beneficiary Election" is pre selected as default value. By pals on Oct 24th 2007 'lstEnrollmentSourceCode.SelectedValue = "B" 'lstEnrollmentSourceCode.Items.Insert(0, New ListItem("Select", "0")) Catch ex As Exception errHandle.gProcHandleErrors(ex, Session("MemberID"), "SPStatus.aspx.vb, gprocFillSEPCode") Throw ex Finally lobjCommon = Nothing ///here the error occurs as 'NullException was unhandle by the user code' errHandle = Nothing End Try End Sub

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  • errorPage directive works, but error-page in web.xml doesn't?

    - by danb
    I get jsp exceptions causing a forward to my error page when I put this at the top of my JSPs... <%@ page errorPage="/error.page" %> but when I try to do it globally with web.xml like so: <error-page> <exception-type>java.lang.Throwable</exception-type> <location>/error.page</location> </error-page> I just get a blank page... I've also tried putting /error.jsp in the location element.. but no love with that either.. I am triggering an exception with a jsp that just contains this: <%if(true)throw new RuntimeException("test exception");%> I do see the exception in the console from tomcat but I just can't get that error page to show without a directive on every jsp... am I missing something simple here?

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  • How to work with delegates and event handler for user control.

    - by Shantanu Gupta
    I have created a user control that contains a button. I am using this control on my winform which will be loaded at run time after fetching data from database. Now I need to remove a row from a datatable on the Click event of that button. The problem is that how do I capture that event in my form. Currently it goes in that user control's btn click event defination.

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  • related to list and file handling?

    - by kaushik
    i have file with contents in list form such as [1,'ab','fgf','ssd'] [2,'eb','ghf','hhsd'] [3,'ag','rtf','ssfdd'] i want to read that file line by line using f.readline and assign thn to a list so as to use it is the prog as a list for using list properties tried like k=[ ] k=f.readline() print k[1] i xpected a result to show 2nd element in the list in first line but it showed the first bit and gave o/p as '1' how to get the xpected output.. please suggest

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  • What is the best way to log errors in Zend Framework in my project at this stage?

    - by Pasta
    We built an app in Zend Framework and have not worked a lot in setting up error reporting and logging. Is there any way we could get some level or error reporting without too much change in the code? Is there a ErrorHandler plugin available? The basic requirement is to log errors that happens within the controller, missing controllers, malformed URLs, etc. I also want to be able to log errors within my controllers. Will using error controller here, help me identify and log errors within my controllers? How best to do this with minimal changes?

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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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  • why cannot use uncaught_exception in dtor?

    - by camino
    Hi , Herb Sutter in his article http://www.gotw.ca/gotw/047.htm pointed out that we cannot use uncaught_exception in desturctor function, // Why the wrong solution is wrong // U::~U() { try { T t; // do work } catch( ... ) { // clean up } } If a U object is destroyed due to stack unwinding during to exception propagation, T::~T will fail to use the "code that could throw" path even though it safely could. but I write a test program, and T::~T in fact didn't use the "code that could throw" #include <exception> #include <iostream> using namespace std; class T { public: ~T() { if( !std::uncaught_exception() ) { cout<<"can throw"<<endl; throw 1; } else { cout<<"cannot throw"<<endl; } } }; struct U { ~U() { try { T t; } catch( ... ) { } } }; void f() { U u; throw 2; } int main() { try { f(); } catch(...) {} } output is : cannot throw did I miss something? Thanks

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  • Long key press handling in android 1.5

    - by Kaillash
    Hi, I want to handle key press and long key press for the key code KEYCODE_BACK(back button). can any one suggest me how to do this in android 1.5(API level 3). Here is the code. public boolean onKeyDown(int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_BACK) { if(event.getRepeatCount()==0) { // normal key press // But problem is, this code is hitting for long press also, how to avoid this } else { // Long key press //Do something here } // Always consume back key event by returning true //so that default behavior of back is overrided return true; } return super.onKeyDown(keyCode, event); }

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  • error handling on browser

    - by godistrue
    hi guys.. presently im developing my own website named justclickme.com this website which is everything works fine but am getting this errror Notice: Undefined variable: body in E:\wamp\www\jcme\email-order-form.php on line 60 here is my code $to = sendmail_single_field_orderform($sessionid,'emailid'); $subject = just click me.'; $body .= "<html><title>SPS Mobile Services</title></body>";->here only am getting error $body .= "<table width='100%' border='0' cellspacing='0' cellpadding='0'>"; can any one help me thanks

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  • How to further improve error messages in Scala parser-combinator based parsers?

    - by rse
    I've coded a parser based on Scala parser combinators: class SxmlParser extends RegexParsers with ImplicitConversions with PackratParsers { [...] lazy val document: PackratParser[AstNodeDocument] = ((procinst | element | comment | cdata | whitespace | text)*) ^^ { AstNodeDocument(_) } [...] } object SxmlParser { def parse(text: String): AstNodeDocument = { var ast = AstNodeDocument() val parser = new SxmlParser() val result = parser.parseAll(parser.document, new CharArrayReader(text.toArray)) result match { case parser.Success(x, _) => ast = x case parser.NoSuccess(err, next) => { tool.die("failed to parse SXML input " + "(line " + next.pos.line + ", column " + next.pos.column + "):\n" + err + "\n" + next.pos.longString) } } ast } } Usually the resulting parsing error messages are rather nice. But sometimes it becomes just sxml: ERROR: failed to parse SXML input (line 32, column 1): `"' expected but `' found ^ This happens if a quote characters is not closed and the parser reaches the EOT. What I would like to see here is (1) what production the parser was in when it expected the '"' (I've multiple ones) and (2) where in the input this production started parsing (which is an indicator where the opening quote is in the input). Does anybody know how I can improve the error messages and include more information about the actual internal parsing state when the error happens (perhaps something like a production rule stacktrace or whatever can be given reasonably here to better identify the error location). BTW, the above "line 32, column 1" is actually the EOT position and hence of no use here, of course.

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  • How can a client gracefully detect when a server disconnects?

    - by Ummar
    I am working on a client-server application. The client continuously reads data from server, so when a server is closed or disconnects then the client crashes. I tried a try/catch block, but it didn't work. My client application is written in C++. I want the client to display some proper message like "Server disconnected," then exit.

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  • How to prevent users from typing incorrect inputs ?

    - by ZaZu
    Hello, I want the program to loop a scan function if the user types anything else other than numbers.. My code is : do{ printf("Enter rows\n"); scanf("%d",&row); }while(row>='a' && row<='z'); but this code doesnt work .. I keep getting an error when typing in a letter. I tried manipulating around it and the whole thing loops infinitely ... What am I doing wrong ? Please help thanks !

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  • Throwing exception or retuning value

    - by user274737
    I am using another service in a Service Oriented Architecture. My service used the other service to save data into the database. Is is good practice for me to rethrow the exception which i get from save service or should i catch the exception and encapsulate it in my result and then just send the result back.

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