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  • passing Perl method results as a reference

    - by arareko
    Some XML::LibXML methods return arrays instead of references to arrays. Instead of doing this: $self->process_items($xml->findnodes('items/item')); I want to do something like: $self->process_items(\$xml->findnodes('items/item')); So that in process_items() I can dereference the original array instead of creating a copy: sub process_items { my ($self, $items) = @_; foreach my $item (@$items) { # do something... } } I can always store the results of findnodes() into an array and then pass the array reference to my own method, but let's say I want to try a reduced version of my code. Is that the correct syntax for passing the method results or should I use something different? Thanks!

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  • Is it guaranteed that new Integer(i) == i in Java?

    - by polygenelubricants
    Consider the following snippet: int i = 99999999; byte b = 99; short s = 9999; Integer ii = Integer.valueOf(9); // should be within cache System.out.println(new Integer(i) == i); // "true" System.out.println(new Integer(b) == b); // "true" System.out.println(new Integer(s) == s); // "true" System.out.println(new Integer(ii) == ii); // "false" It's obvious why the last line will ALWAYS prints "false": we're using == reference identity comparison, and a new object will NEVER be == to an already existing object. The question is about the first 3 lines: are those comparisons guaranteed to be on the primitive int, with the Integer auto-unboxed? Are there cases where the primitive would be auto-boxed instead, and reference identity comparisons are performed? (which would all then be false!)

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  • Linking Error: undefined reference to `MPI_Init' on Windows 7

    - by fatpipp
    I am using OpenMPI library to write a program to run on Windows 7. I compile and build with C Free 4.0, Mingw. Compiling is Ok but when the compiler links object, errors "undefined reference to ..." occurs. I have set the environment already: I added OpenMPI lib, include and bin folder into C Free Build Directories. I added them into Windows environment variables too. But the error still occurs. Can anyone tell me how to fix it? Thanks a lot.

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  • Proper usage of Java Weak Reference in case of nested collections

    - by Tong Wang
    I need to define a weak reference Map, whose value is a Set. I use Google collections' MapMaker, like this: Map<Class<? extends Object>, Set<Foo>> map = new MapMaker().weakKeys().weakValues().makeMap(); So, for Set<Foo>, can I use a normal HashSet? Or, do I have to create a weak HashSet, like this: Collections.newSetFromMap(new WeakHashMap<Foo, Boolean>()); And why? Another question, the key of my map is Class objects, when will a Class object become weakly reachable? In other words, what is the lifetime of a Class object? Thanks.

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  • How do you reference another element in a xaml list

    - by Ball
    I'm using xaml as a datastore because It's quick and we haven't yet defined a file format. But I can only seem to create xaml that is a pure tree, even if it is acyclic. I know how to create a list of items in xaml, but How do I share objects in two lists? Below is an example of what I'm trying to say. <CreaturFile> <CreatureFile.Monsters> <Monster Name="Kobold" x:Name="Mepo"/> <Monster Name="Goblin"/> </CreatureFile.Monsters> <CreatureFile.Encounters> <Encounter> <Reference ElementName="Mepo"/> </Encounter> </CreatureFile.Encounters> </CreatureFile>

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  • ASP.NET null reference exception

    - by nanek
    Please help me to figure out what is wrong with this code: I have ASP.NET page with one button visible. When user clicks it - it instances MyClass (its implementation is in AppCode directory) and turns invisible (button2 becomes visible). When I click button2 it raises "Object reference not set to an instance of an object" Exception. What seems to be the problem? { public MyClass noviTest; protected void Page_Load(object sender, EventArgs e) { } protected void Button1_Click(object sender, EventArgs e) { noviTest = new MyClass(TextBox1.Text); Button1.Visible = false; Button2.Visible = true; } protected void Button2_Click(object sender, EventArgs e) { Label1.Text=noviTest.getID; //this is the critical line } } Thank You in advance, Regards

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  • Table character encoding - exception in application

    - by zgnilec
    I have a code: CREATE TABLE IF NOT EXISTS Person ( name varchar(24) ... ) CHARACTER SET utf8 COLLATE utf8_polish_ci; This works OK in my application, but I read if someone put in name field a string that contains character wchich code is greater than 127, database will use 2 bytes (or more) to store this character. So i think, i will change character set to utf16: CHARACTER SET utf16 COLLATE utf16_polish_ci; But now when I run my application, exception apears: KeyNotFoundException. It apears exactly at these instructions: MySqlCommand komenda = baza.Polaczenie.CreateCommand (); komenda.CommandText = zapytanie; MySqlDataReader dr = komenda.ExecuteReader (); // HERE, at execute reader method if (dr.Read ()) ... 1) Anyone had similar problem? 2) Any idea how to use always 2 bytes/char in database field?

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  • Basic class returns object reference instead of Array

    - by php-b-grader
    I have very basic class: class Customer { protected $id; protected $customer; public function __construct($customer_id) { $this->id = $customer_id; return $this->set_customer(); } protected function set_customer() { $query = mysql_query("SELECT * FROM customer WHERE id = '$this->id'"); $this->customer = mysql_fetch_row($query); return $this->customer; } } $customer = new Customer($order->customer->id); print_r($customer); This is not doing what I want it to but I understand why... $customer returns a reference to the Customer Object... What I want is the MySQL row array from the mysql_fetch_row() - How do I return the array? What am I missing?

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  • How does one refer to the game1 class's variables in XNA

    - by user1149068
    I try to refer to an array in the Game1 class by creating an object of the Game1 class with its definition Game1 gameObject; , its declaration gameObject = new Game1(); in the constructor, and its usage gameObject.tileArray[xInt, yInt].treed = true;. The game1 class itself remains unchanged in its class code other than some methods and variables. When I try to use this code in the TreeRegion class it gives me "Object reference not set to an instance of an object," leading me to believe that the game1 class is null somehow. How might one change the class or object in order to refer to game1's variables? Mind you I am self-taught and still rather new to C#. The class that refers to game1: http://pastebin.com/0chEcKfq Game1 itself http://pastebin.com/zLDVzCca

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  • When to use try/catch

    - by coffeeaddict
    I'm always finding myself wanting to put a try/catch around the lets say Business Layer methods. But I feel though that I don't need a try/catch if I'm simply rethrowing it up to the Presentation Layer. Is that right? I should not be rethrowing an exception from code that's wrapped in a try/catch in a BL method and should be letting the caller which would be from the Presentation Layer code be using a try/catch to handle it there? The BL method will throw an error without the try/catch anyway..the compiler will. So it wouldn't make sense to use a try/catch in a BL method that's to be consumed by a layer higher up correct?

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  • how to avoid temporaries when copying weakly typed object

    - by Truncheon
    Hi. I'm writing a series classes that inherit from a base class using virtual. They are INT, FLOAT and STRING objects that I want to use in a scripting language. I'm trying to implement weak typing, but I don't want STRING objects to return copies of themselves when used in the following way (instead I would prefer to have a reference returned which can be used in copying): a = "hello "; b = "world"; c = a + b; I have written the following code as a mock example: #include <iostream> #include <string> #include <cstdio> #include <cstdlib> std::string dummy("<int object cannot return string reference>"); struct BaseImpl { virtual bool is_string() = 0; virtual int get_int() = 0; virtual std::string get_string_copy() = 0; virtual std::string const& get_string_ref() = 0; }; struct INT : BaseImpl { int value; INT(int i = 0) : value(i) { std::cout << "constructor called\n"; } INT(BaseImpl& that) : value(that.get_int()) { std::cout << "copy constructor called\n"; } bool is_string() { return false; } int get_int() { return value; } std::string get_string_copy() { char buf[33]; sprintf(buf, "%i", value); return buf; } std::string const& get_string_ref() { return dummy; } }; struct STRING : BaseImpl { std::string value; STRING(std::string s = "") : value(s) { std::cout << "constructor called\n"; } STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } bool is_string() { return true; } int get_int() { return atoi(value.c_str()); } std::string get_string_copy() { return value; } std::string const& get_string_ref() { return value; } }; struct Base { BaseImpl* impl; Base(BaseImpl* p = 0) : impl(p) {} ~Base() { delete impl; } }; int main() { Base b1(new INT(1)); Base b2(new STRING("Hello world")); Base b3(new INT(*b1.impl)); Base b4(new STRING(*b2.impl)); std::cout << "\n"; std::cout << b1.impl->get_int() << "\n"; std::cout << b2.impl->get_int() << "\n"; std::cout << b3.impl->get_int() << "\n"; std::cout << b4.impl->get_int() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_ref() << "\n"; std::cout << b2.impl->get_string_ref() << "\n"; std::cout << b3.impl->get_string_ref() << "\n"; std::cout << b4.impl->get_string_ref() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_copy() << "\n"; std::cout << b2.impl->get_string_copy() << "\n"; std::cout << b3.impl->get_string_copy() << "\n"; std::cout << b4.impl->get_string_copy() << "\n"; return 0; } It was necessary to add an if check in the STRING class to determine whether its safe to request a reference instead of a copy: Script code: a = "test"; b = a; c = 1; d = "" + c; /* not safe to request reference by standard */ C++ code: STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } If was hoping there's a way of moving that if check into compile time, rather than run time.

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  • Scala : reference is ambiguous (imported twice)

    - by tk
    I want to use a method as a parameter of another method of the same class. I have a class and objects which are companions: class mM(var elem:Matrix){ //apply a function on a dimension rows (1) or cols (2) def app(func:Iterable[Double]=>Double)(dim : Int) : Matrix = { ... } //utility function def logsumexp(): Double = {...} } object mM{ def apply(elem:Matrix):mM={new mM(elem)} def logsumexp(elem:Iterable[Double]): Double ={ this.apply(elem.asInstanceOf[Matrix]).logsumexp() } } Normally I use logsumexp like this mM(matrix).logsumexp but if want to apply it to the rows I can't use mM(matrix).app(mM.logsumexp)(1), I get the error: error: reference to mM is ambiguous; it is imported twice in the same scope by import mM and import mM What is the most elegant solution ? Should I change logsumexp() to another class ? Thanks,=)

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  • How to extract object reference from property access lamda

    - by Jim C
    Here's a follow-up question to http://stackoverflow.com/questions/2820660/get-name-of-property-as-a-string. Given a method Foo (error checking omitted for brevity): // Example usage: Foo(() => SomeClass.SomeProperty) // Example usage: Foo(() => someObject.SomeProperty) void Foo(Expression<Func<T>> propertyLambda) { var me = propertyLambda.Body as MemberExpression; var pi = me.Member as PropertyInfo; bool propertyIsStatic = pi.GetGetMethod().IsStatic; object owner = propertyIsStatic ? me.Member.DeclaringType : ???; ... // Execute property access object value = pi.GetValue(owner, null); } I've got the static property case working but don't know how to get a reference to someObject in the instance property case. Thanks in advance.

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  • update value of a variable outside a class in VB.NET

    - by dpp
    I have a class derived from a Form, it has textbox for username and password and an OK button. I want it to behave like an InputBox so I can use it like this: Dim Username As String = "" Dim Password As String = "" Dim authorization As New Authorization(Username, Password) authorization.ShowDialog() 'The user will click OK and I will expect the Username and Password to change based on the user input MsgBox(Username & " " & Password) The Authorization class: Public Class Authorization Dim RefUsername As String Dim RefPassword As String Public Sub New(ByRef Username As String, ByRef Password As String) InitializeComponent() RefUsername = Username 'I'm trying to pass reference instead of value RefPassword = Password 'I'm trying to pass reference instead of value End Sub Private Sub OKButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles AuthorizeButton.Click RefUsername = Username.Text 'I'm trying to change value of variable outside the class RefPassword = Password.Text 'I'm trying to change value of variable outside the class Me.Close() End Sub End Class In short, I want to change the value of variables outside the class when the user clicks the OK, how am I going to accomplish that?

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  • Checking exception before using GETITEMBYID()

    - by ps123
    Hello, I am getting item by getiembyid...but I want to check before using it that whether item exist or not...I don't want to use query as main purpose of using Getitembyid is performance.....any idea how to achieve this... itemid = Response.QueryString["loc"]; SPList mylist = myweb.GetList(SPUrlUtility.CombineUrl(myweb.ServerRelativeUrl, "/Lists/Location")); //now id itemid does not exist it throws exception...so i want to check before using following statement that itemid exist...I know i can check throw SPQuery but as i said above because of performance issue only i m using itemid.... SPListItem myitem = mylist.GetItemById(Convert.ToInt32(itemid)); Any idea how to achieve this?

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  • Java Null Pointer Exception :-(

    - by John-Michael Reed
    I've got a Null Pointer Exception in my main that just won't go away and I'm totally out of ideas. The error is on the line "Board[x][y].color = 2;" in which Board is a public, static array of piece objects that contain instance variables like the one "color" that is being set to 2 in the above statement. Pieces is not static - that is there are many different copies of pieces, each with its own data, but only one board. The array has been initialized and defined as both public Piece[][] Board = new Piece[8][8] and public static Piece[][] Board = new Piece[8][8], but no matter how I mess around with it (getting rid of static, putting the variable in another object, etc.), I can't seem to get the error to go away. Help?

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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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  • ADO.NET DataService Exception

    - by Ravi
    Hi, I am working on C#.Net with ADO.NET Dataservice. I try to update one record to relational tabel, when I reach context.SetLink() I am getting exception("The context is not currently tracking the entity"). I don't know how to solve this problem. My code is specified below. LogNote dbLogNote =logNote; LogSubSession dbLogSubSession = (from p in context.LogSubSession where p.UID == logNote.SubSessionId select p).First<LogSubSession>() as LogSubSession; context.AddToLogNote(dbLogNote); dbLogNote.LogSubSession = dbLogSubSession; context.SetLink(dbLogNote, "LogSubSession", dbLogSubSession); context.SaveChanges(); Here LogSubSession is a primary table and LogNote is a foreign table. I am updating data into foreign table based on primary key table. Thanks

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  • problem with exporting a customized form from dll

    - by mavric
    I'm working on an application so i have write an dll which contain a form with some additional work and methods. so in the beginning of my program the thread launch this form (from my dll) to get some informations and then hide it and initialize some components and the application form and then show it. when the thread come the line where it define new instance of the exported form "MyForm inputform = new MyForm();" it throw an Exception called "Top-level control cannot be added to a control." so i don't know what to do ?!!. i tried to take the code of the form from the dll source code and put it in the main program and it works.... .but still i want to know what happen and what impede my application from run that form from my dll. thanks.

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  • Is there a way to force JUnit to fail on ANY unchecked exception, even if swallowed

    - by Uri
    I am using JUnit to write some higher level tests for legacy code that does not have unit tests. Much of this code "swallows" a variety of unchecked exceptions like NullPointerExceptions (e.g., by just printing stack trace and returning null). Therefore the unit test can pass even through there is a cascade of disasters at various points in the lower level code. Is there any way to have a test fail on the first unchecked exception even if they are swallowed? The only alternative I can think of is to write a custom JUnit wrapper that redirects System.err and then analyzes the output for exceptions.

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  • [PersistenceException: org.hibernate.exception.SQLGrammarException: could not execute query]

    - by doniyor
    i need help. i am trying to select from database thru sql statement in play framework, but it gives me error, i cannot figure out where the clue is. here is the code: @Transactional public static Users findByUsernameAndPassword(String username, String password){ String hash = DigestUtils.md5Hex(password); Query q = JPA.em().createNativeQuery("select * from USERS where" + "USERNAME=? and PASSWORD=?").setParameter(1, username).setParameter(2, password); List<Users> users = q.getResultList(); if(users.isEmpty()){ return null; } else{ return users.get(0); here is the eror message: [PersistenceException: org.hibernate.exception.SQLGrammarException: could not execute query] can someone help me please! any help i would appreciate! thanks

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  • Circular reference while setting up bidirectional communication line between two remote objects

    - by mphair
    I'm using .Net remoting to set up a bidirectional communication line between two objects. The basic structure is as follows: Instances of RemoteObjectA call methods on StaticObjectA. Instances of RemoteObjectB call methods on StaticObjectB. StaticObjectA needs to be able to call methods provided by RemoteObjectB. StaticObjectB needs to be able to call methods provided by RemoteObjectA. The problem with this setup is the circular reference in RemoteObjectA gets StaticObjectA gets RemoteObjectB gets StaticObjectB gets RemoteObjectA... I implemented an interface IRemoteObjectA and IRemoteObjectB and had the remote objects inheret from their respective interfaces, but then setting up the remoting fails. If the solution to this problem is: "don't use remoting", I can deal with that. Just wanted to make sure I wasn't missing a simple solution.

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  • c# - best way to initialize an array of reference type object

    - by lidong
    I wonder if there is better way to initialize an array of reference type object, like this. Queue<int>[] queues = new Queue<int>[10]; for (int i = 0; i < queues.Length; i++) { queues[i] = new Queue<int>(); } I tried Enumerable.Repeat, but all elements in the array refer to same instance, Queue<int>[] queues = Enumerable.Repeat(new Queue<int>(), 10).ToArray(); I also tried Array.ForEach, but it doesn't work without ref keyword: Queue<int>[] queues = Array.ForEach(queues, queue => queue = new Queue<int>()); any other idea?

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  • CMD Execption Handling C/C++

    - by ciyo
    I will use some CMD commands in my program and these commands might throw some exceptions. And as you know, when an exception accours, CMD writes its own error message the screen. But, I want to write my own error message. My question is this: Is there a way to block CMD messages and write only my own error messages? P.S. This is not a complex program. It executes CMD commands using System(). Example: Let's say, the user can rename and copy any files in the program. As you know, if the user does not enter file's path properly, an error message is showed on the screen. And I want that this error message never appears on the screen. Only my own error message is showed. Thank you!

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  • Exception during processing XSLT transformation!

    - by Artic
    I'm using this code to generate contents file. try { StreamResult result = new StreamResult(); TransformerFactory tf = TransformerFactory.newInstance(); Templates templ = tf.newTemplates(xsltSource); Transformer transf = templ.newTransformer(); for (String item: groups){ item = item.replaceAll(" ", "-").toLowerCase(); result.setOutputStream(new FileOutputStream(path+item+".html")); transf.clearParameters(); transf.setParameter("group", item); transf.transform(xmlSource, result); } } catch (TransformerConfigurationException e) { throw new SinkException(e.getMessage()); } catch (TransformerException e) { throw new SinkException(e.getMessage()); } But on second iteration I have an exception ERROR: javax.xml.transform.TransformerException: com.sun.org.apache.xml.internal.utils.WrappedRuntimeException: Read error Cann't understand what is the reason?

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