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  • Catching a nested-in-template exception [C++]

    - by Karol
    Hello, I have a problem with writing a catch clause for an exception that is a class nested in a template. To be more specific, I have a following definition of the template and exception: /** Generic stack implementation. Accepts std::list, std::deque and std::vector as inner container. */ template < typename T, template < typename Element, typename = std::allocator<Element> > class Container = std::deque > class stack { public: class StackEmptyException { }; ... /** Returns value from the top of the stack. Throws StackEmptyException when the stack is empty. */ T top() const; ... } I have a following template method that I want exception to catch: template <typename Stack> void testTopThrowsStackEmptyExceptionOnEmptyStack() { Stack stack; std::cout << "Testing top throws StackEmptyException on empty stack..."; try { stack.top(); } catch (Stack::StackEmptyException) { // as expected. } std::cout << "success." << std::endl; } When I compile it (-Wall, -pedantic) I get the following error: In function ‘void testTopThrowsStackEmptyExceptionOnEmptyStack()’: error: expected type-specifier error: expected unqualified-id before ‘)’ token === Build finished: 2 errors, 0 warnings === Thanks in advance for any help! What is interesting, if the stack implementation was not a template, then the compiler would accept the code as it is.

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  • Detecting a Dispose() from an exception inside using block

    - by Augusto Radtke
    I have the following code in my application: using (var database = new Database()) { var poll = // Some database query code. foreach (Question question in poll.Questions) { foreach (Answer answer in question.Answers) { database.Remove(answer); } // This is a sample line that simulate an error. throw new Exception("deu pau"); database.Remove(question); } database.Remove(poll); } This code triggers the Database class Dispose() method as usual, and this method automatically commits the transaction to the database, but this leaves my database in an inconsistent state as the answers are erased but the question and the poll are not. There is any way that I can detect in the Dispose() method that it being called because of an exception instead of regular end of the closing block, so I can automate the rollback? I don´t want to manually add a try ... catch block, my objective is to use the using block as a logical safe transaction manager, so it commits to the database if the execution was clean or rollbacks if any exception occured. Do you have some thoughts on that?

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  • Can I automatically throw descriptive exceptions with parameter values and class feild information?

    - by Robert H.
    I honestly don't throw exceptions often. I catch them even less, ironically. I currently work in shop where we let them bubble up to avicode. For whatever reason, however, avicode isn't configured to capture some of the critical bits I need when these exceptions come bouncing back to my attention. Specifically, I'd like to see the parameter values and the class’s field data at the time of the exception. I’d guess with the large suite of .Net services that I could create a static method to crawl up the stack, gather these bits and store them in a string that I could stick in my exception message. I really don't are how long such a method would take to execute as performance is no longer a concern when I hit one of these scenarios. If it's possible, I'm sure someone has done it. If that's the case, I'm having a hard time finding it. I think any search containing "exception" brings back too many resutls. Anyway, can this be done? If so, some examples or links would be great. Thanks in advance for your time, Robert

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  • java servlet:response.sendRedirect() not giving illegal state exception if called after commit of re

    - by sahil garg
    after commit of response as here redirect statement should give exception but it is not doing so if this redirect statemnet is in if block.but it does give exception in case it is out of if block.i have shown same statement(with marked stars ) at two places below.can u please tell me reason for it. protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub synchronized (noOfRequests) { noOfRequests++; } PrintWriter pw=null; response.setContentType("text/html"); response.setHeader("foo","bar"); //response is commited because of above statement pw=response.getWriter(); pw.print("hello : "+noOfRequests); //if i remove below statement this same statement is present in if block.so statement in if block should also give exception as this one do, but its not doing so.why? ***response.sendRedirect("http://localhost:8625/ServletPrc/login% 20page.html"); if(true) { //same statement as above ***response.sendRedirect("http://localhost:8625/ServletPrc/login%20page.html"); } else{ request.setAttribute("noOfReq", noOfRequests); request.setAttribute("name", new Name().getName()); request.setAttribute("GmailId",this.getServletConfig().getInitParameter("GmailId") ); request.setAttribute("YahooId",this.getServletConfig().getInitParameter("YahooId") ); RequestDispatcher view1=request.getRequestDispatcher("HomePage.jsp"); view1.forward(request, response); } }

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  • Weird exception: Cannot cast String to Boolean when using getBoolean

    - by La bla bla
    I'm getting a very weird error. I have 2 activities. On both I'm getting the SharedPreferences using MODE_PRIVATE (if it matters) by sp = getPreferences(MODE_PRIVATE); on each activity's onCreate() I'm calling sp.getBoolean(IntroActivity.SHOW_INTRO, true) On the IntroActivity this works fine. But when I'm trying in the main activity, I'm getting this 10-12 04:55:23.208: E/AndroidRuntime(11668): FATAL EXCEPTION: main 10-12 04:55:23.208: E/AndroidRuntime(11668): java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Boolean 10-12 04:55:23.208: E/AndroidRuntime(11668): at android.app.SharedPreferencesImpl.getBoolean(SharedPreferencesImpl.java:242) 10-12 04:55:23.208: E/AndroidRuntime(11668): at com.lablabla.parkme.ParkMeActivity$2.onClick(ParkMeActivity.java:194) 10-12 04:55:23.208: E/AndroidRuntime(11668): at android.view.View.performClick(View.java:4084) 10-12 04:55:23.208: E/AndroidRuntime(11668): at android.view.View$PerformClick.run(View.java:16966) 10-12 04:55:23.208: E/AndroidRuntime(11668): at android.os.Handler.handleCallback(Handler.java:615) 10-12 04:55:23.208: E/AndroidRuntime(11668): at android.os.Handler.dispatchMessage(Handler.java:92) 10-12 04:55:23.208: E/AndroidRuntime(11668): at android.os.Looper.loop(Looper.java:137) 10-12 04:55:23.208: E/AndroidRuntime(11668): at android.app.ActivityThread.main(ActivityThread.java:4745) 10-12 04:55:23.208: E/AndroidRuntime(11668): at java.lang.reflect.Method.invokeNative(Native Method) 10-12 04:55:23.208: E/AndroidRuntime(11668): at java.lang.reflect.Method.invoke(Method.java:511) 10-12 04:55:23.208: E/AndroidRuntime(11668): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 10-12 04:55:23.208: E/AndroidRuntime(11668): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 10-12 04:55:23.208: E/AndroidRuntime(11668): at dalvik.system.NativeStart.main(Native Method) I made sure that I'm not putting a String somewhere in the middle with that same key Any ideas? Thanks! EDIT: some code: //onCreate() sp = getPreferences(MODE_PRIVATE); // other method boolean showIntro = sp.getBoolean(IntroActivity.SHOW_INTRO, true); // Exception is here showIntroCheckBox.setChecked(showIntro); If it matters, the code which throws the exception is inside a button's onClick

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  • Is there an "opposite" to the null coalescing operator? (…in any language?)

    - by Jay
    null coalescing translates roughly to return x, unless it is null, in which case return y I often need return null if x is null, otherwise return x.y I can use return x == null ? null : x.y; Not bad, but that null in the middle always bothers me -- it seems superfluous. I'd prefer something like return x :: x.y;, where what follows the :: is evaluated only if what precedes it is not null. I see this as almost an opposite to null coalescence, kind of mixed in with a terse, inline null-check, but I'm [almost] certain that there is no such operator in C#. Are there other languages that have such an operator? If so, what is it called? (I know that I can write a method for it in C#; I use return NullOrValue.of(x, () => x.y);, but if you have anything better, I'd like to see that too.)

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  • Fluent NHibernate - subclasses with shared reference

    - by ollie
    Edit: changed class names. I'm using Fluent NHibernate (v 1.0.0.614) automapping on the following set of classes (where Entity is the base class provided in the S#arp Architecture framework): public class Car : Entity { public virtual int ModelYear { get; set; } public virtual Company Manufacturer { get; set; } } public class Sedan : Car { public virtual bool WonSedanOfYear { get; set; } } public class Company : Entity { public virtual IList<Sedan> Sedans { get; set; } } This results in the following Configuration (as written to hbm.xml): <class name="Company" table="Companies"> <id name="Id" type="System.Int32" unsaved-value="0"> <column name="`ID`" /> <generator class="identity" /> </id> <bag cascade="all" inverse="true" name="Sedans" mutable="true"> <key> <column name="`CompanyID`" /> </key> <one-to-many class="Sedan" /> </bag> </class> <class name="Car" table="Cars"> <id name="Id" type="System.Int32" unsaved-value="0"> <column name="`ID`" /> <generator class="identity" /> </id> <property name="ModelYear" type="System.Int32"> <column name="`ModelYear`" /> </property> <many-to-one cascade="save-update" class="Company" name="Manufacturer"> <column name="`CompanyID`" /> </many-to-one> <joined-subclass name="Sedan"> <key> <column name="`CarID`" /> </key> <property name="WonSedanOfYear" type="System.Boolean"> <column name="`WonSedanOfYear`" /> </property> </joined-subclass> </class> So far so good! But now comes the ugly part. The generated database tables: Table: Companies Columns: ID (PK, int, not null) Table: Cars Columns: ID (PK, int, not null) ModelYear (int, null) CompanyID (FK, int, null) Table: Sedan Columns: CarID (PK, FK, int, not null) WonSedanOfYear (bit, null) CompanyID (FK, int, null) Instead of one FK for Company, I get two! How can I ensure I only get one FK for Company? Override the automapping? Put a convention in place? Or is this a bug? Your thoughts are appreciated.

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  • A null value should be considered as 0 when addition of it is done with decimal value.

    - by Harikrishna
    There are three column in the datatable A,B and C. Now each column is type of decimal. Now I am doing like dt.Columns["A"].Expression="B+C"; to make addition of Column B's record and column C's record. Now if there is any value of B or C is null then addition of B and C will be null like B's value is 3 and C's value is null for first row then B+C(3+null) will be null which is not appropriate, the result of addition should be 3.If I replace 0 instead of null then it will be ok.But whereever there is null value in the records it should be remain it is and it should not be replaced by 0.That is null value should not be replaced by 0 and when addition of null value is done with any decimal value null value should be considered as 0. Is it possible,how can we do this ?

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  • Good reference for Cisco Resilient Ethernet Protocol

    - by Karthik
    I have been trying to understand Cisco's Resilient Ethernet Protocol, but am unable to find a proper source to read from. I checked the Cisco site and also their White Paper on REP. But none of them helped to understand REP clearly. Googling was also of not much help, as all I got was explanation about configuration instructions and not on the protocol itself. Can you guys point me to a good book or site, which explains Resilient Ethernet Protocol in detail? Thanks in advance.

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  • Can PCRE regex match a null character?

    - by Keng
    I have a text source with nulls in it and I need to pull them out along with my regex pattern. Can regex even match a null character? I only realized I had them when my pattern refused to match and when I pasted it into Notepad++ it showed all the null characters.

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  • Mysql Left Join Null Result

    - by Ozzy
    I have this query SELECT articles.*, users.username AS `user` FROM `articles` LEFT JOIN `users` ON articles.user_id = users.id ORDER BY articles.timestamp Basically it returns the list of articles and the username that the article is associated to. Now if there is no entry in the users table for a particular user id, the users var is NULL. Is there anyway to make it that if its null it returns something like "User Not Found"? or would i have to do this using php?

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  • Can a constructor return a NULL value?

    - by Sanctus2099
    I know constructors don't "return" anything but for instance if I call CMyClass *object = new CMyClass() is there any way to make object to be NULL if the constructor fails? In my case I have some images that have to be loaded and if the file reading fails I'd like it to return null. Is there any way to do that? Thanks in advance.

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  • Checking for a null int value from a Java ResultSet

    - by ian_scho_es
    In Java I'm trying to test for a null value, from a ResultSet, where the column is being cast to a primitive int type. int iVal; ResultSet rs = magicallyAppearingStmt.executeQuery(query); if (rs.next()) { if (rs.getObject("ID_PARENT") != null && !rs.wasNull()) { iVal = rs.getInt("ID_PARENT"); } } From the code fragment above, is there a better way to do this, and I assume that the second wasNull() test is redundant? Educate us, and Thanks

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  • Is null a class in java?

    - by Somerandomeguy
    According to, http://www.freshvanilla.org:8080/display/www/Java+Interview+Questions Under, Which class is the superclass of every class? null seems to be the answer. I found that new Object().getClass().getSuperClass() verifies the answer as correct. But can null be considered a class? I see all primitive data types are represented as Class objects from java[dot]sun.com/j2se/1.4.2/docs/api/java/lang/Class.html

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  • return value (not a reference) from the function, bound to a const reference in the calling function

    - by brainydexter
    "If you return a value (not a reference) from the function, then bind it to a const reference in the calling function, its lifetime would be extended to the scope of the calling function." So: const BoundingBox Player::GetBoundingBox(void) { return BoundingBox( &GetBoundingSphere() ); } Returns a value of type const BoundingBox from function GetBoundingBox() Called function: (From within function Update() the following is called:) variant I: (Bind it to a const reference) const BoundingBox& l_Bbox = l_pPlayer->GetBoundingBox(); variant II: (Bind it to a const copy) const BoundingBox l_Bbox = l_pPlayer->GetBoundingBox(); Both work fine and I don't see the l_Bbox object going out of scope. (Though, I understand in variant one, the copy constructor is not called and thus is slightly better than variant II). Also, for comparison, I made the following changes. BoundingBox Player::GetBoundingBox(void) { return BoundingBox( &GetBoundingSphere() ); } with Variants: I BoundingBox& l_Bbox = l_pPlayer->GetBoundingBox(); and II: BoundingBox l_Bbox = l_pPlayer->GetBoundingBox(); The objet l_Bbox still does not out scope. So, I don't see how "bind it to a const reference in the calling function, its lifetime would be extended to the scope of the calling function", really extends the lifetime of the object to the scope of the calling function ? Am I missing something trivial here..please explain .. Thanks a lot

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  • C# - Calling ToString() on a Reference Type

    - by nfplee
    Given two object arrays I need to compare the differences between the two (when converted to a string). I've reduced the code to the following and the problem still exists: public void Compare(object[] array1, object[] array2) { for (var i = 0; i < array1.Length; i++) { var value1 = GetStringValue(array1[i]); var value2 = GetStringValue(array2[i]); } } public string GetStringValue(object value) { return value != null && value.ToString() != string.Empty ? value.ToString() : ""; } The code executes fine no matter what object arrays I throw at it. However if one of the items in the array is a reference type then somehow the reference is updated. This causes issues later. It appears that this happens when calling ToString() against the object reference. I have updated the GetStringValue method to the following (which makes sure the object is either a value type or string) and the problem goes away. public string GetStringValue(object value) { return value != null && (value.GetType().IsValueType || value is string) && value.ToString() != string.Empty ? value.ToString() : ""; } However this is just a temporary hack as I'd like to be able to override the ToString() method on my reference types and compare them as well. I'd appreciate it if someone could explain why this is happening and offer a potential solution. Thanks

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  • Failed at linking C++ [undefined reference boost::filesystem3 ... ]

    - by Pphax
    i'm having some troubles compiling my work, i'm using ubuntu with g++! i get a lot of these messages: undefined reference to `boost::filesystem3::directory_entry::m_get_status(boost::system::error_code*) const' undefined reference to `boost::filesystem3::path::extension() const' undefined reference to `boost::filesystem3::path::filename() const' undefined reference to `boost::filesystem3::path::filename() const' (etc...) I've searched and found maaany answers but none of those work for me. [...] -lboost_system (/usr/lib/gcc/i686-linux-gnu/4.4.5/../../../../lib/libboost_system.so) -lboost_filesystem (/usr/lib/gcc/i686-linux-gnu/4.4.5/../../../../lib/libboost_filesystem.so) [...] (when linking it shows those two libraries, i'm guessing the error is related to the second one. hax@lap:~$ locate libboost_filesystem.so /home/hax/boost_1_47_0/bin.v2/libs/filesystem/build/gcc-4.4.5/release/threading-multi/libboost_filesystem.so.1.47.0 /home/hax/boost_1_47_0/stage/lib/libboost_filesystem.so /home/hax/boost_1_47_0/stage/lib/libboost_filesystem.so.1.47.0 /usr/lib/libboost_filesystem.so /usr/lib/libboost_filesystem.so.1.42.0 /usr/local/lib/libboost_filesystem.so /usr/local/lib/libboost_filesystem.so.1.47.0 this is the related line on my makefile: -L. -L../bncsutil/src/bncsutil/ -L../StormLib/stormlib/ -L../boost/lib/ -lbncsutil -lpthread -ldl -lz -lStorm -lmysqlclient_r -lboost_date_time -lboost_thread -lboost_system -lboost_filesystem -Wl -t I tried pointing with -L several different places where i saw filesystem.so was located but it didn't work! Can anyone see the problem in those lines? if you need me to put some extra data i'll do it, i'm not seeing the problem :( Thanks :)

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  • C++ reference variable again!!!

    - by kumar_m_kiran
    Hi All, I think most would be surprised about the topic again, However I am referring to a book "C++ Common Knowledge: Essential Intermediate Programming" written by "Stephen C. Dewhurst". In the book, he quotes a particular sentence (in section under Item 5. References Are Aliases, Not Pointers), which is as below A reference is an alias for an object that already exists prior to the initialization of the reference. Once a reference is initialized to refer to a particular object, it cannot later be made to refer to a different object; a reference is bound to its initializer for its whole lifetime Can anyone please explain the context of "cannot later be made to refer to a different object" Below code works for me, #include <iostream> using namespace std; int main(int argc, char *argv[]) { int i = 100; int& ref = i; cout<<ref<<endl; int k = 2000; ref = k; cout<<ref<<endl; return 0; } Here I am referring the variable ref to both i and j variable. And the code works perfectly fine. Am I missing something? I have used SUSE10 64bit linux for testing my sample program. Thanks for your input in advance.

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  • ASP.NET Error Handling: Creating an extension method to send error email

    - by Jalpesh P. Vadgama
    Error handling in asp.net required to handle any kind of error occurred. We all are using that in one or another scenario. But some errors are there which will occur in some specific scenario in production environment in this case We can’t show our programming errors to the End user. So we are going to put a error page over there or whatever best suited as per our requirement. But as a programmer we should know that error so we can track the scenario and we can solve that error or can handle error. In this kind of situation an Error Email comes handy. Whenever any occurs in system it will going to send error in our email. Here I am going to write a extension method which will send errors in email. From asp.net 3.5 or higher version of .NET framework  its provides a unique way to extend your classes. Here you can fine more information about extension method. So lets create extension method via implementing a static class like following. I am going to use same code for sending email via my Gmail account from here. Following is code for that. using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Net.Mail; namespace Experiement { public static class MyExtension { public static void SendErrorEmail(this Exception ex) { MailMessage mailMessage = new MailMessage(new MailAddress("[email protected]") , new MailAddress("[email protected]")); mailMessage.Subject = "Exception Occured in your site"; mailMessage.IsBodyHtml = true; System.Text.StringBuilder errorMessage = new System.Text.StringBuilder(); errorMessage.AppendLine(string.Format("<B>{0}</B>:{1}<BR/>","Exception",ex.Message)); errorMessage.AppendLine(string.Format("<B>{0}</B>:{1}<BR/>", "Stack Trace", ex.StackTrace)); if (ex.InnerException != null) { errorMessage.AppendLine(string.Format("<B>{0}</B>:{1}<BR/>", " Inner Exception", ex.InnerException.Message)); errorMessage.AppendLine(string.Format("<B>{0}</B>:{1}<BR/>", "Inner Stack Trace", ex.InnerException.StackTrace)); } mailMessage.Body = errorMessage.ToString(); System.Net.NetworkCredential networkCredentials = new System.Net.NetworkCredential("[email protected]", "password"); SmtpClient smtpClient = new SmtpClient(); smtpClient.EnableSsl = true; smtpClient.UseDefaultCredentials = false; smtpClient.Credentials = networkCredentials; smtpClient.Host = "smtp.gmail.com"; smtpClient.Port = 587; smtpClient.Send(mailMessage); } } } After creating an extension method let us that extension method to handle error like following in page load event of page. using System; namespace Experiement { public partial class WebForm1 : System.Web.UI.Page { protected void Page_Load(object sender,System.EventArgs e) { try { throw new Exception("My custom Exception"); } catch (Exception ex) { ex.SendErrorEmail(); Response.Write(ex.Message); } } } } Now in above code I have generated custom exception for example but in production It can be any Exception. And you can see I have use ex.SendErrorEmail() function in catch block to send email. That’s it.. Now it will throw exception and you will email in your email box like below.   That’s its. It’s so simple…Stay tuned for more.. Happy programming.. Technorati Tags: Exception,Extension Mehtod,Error Handling,ASP.NET

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