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  • Declare variables that depend on unknown type in template functions.

    - by rem
    Suppose I'm writing a template function foo that has type parameter T. It gets an object of type T that must have method bar(). And inside foo I want to create a vector of objects of type returned by bar. In GNU C++ I can write something like that: template<typename T> void foo(T x) { std::vector<__typeof(x.bar())> v; v.push_back(x.bar()); v.push_back(x.bar()); v.push_back(x.bar()); std::cout << v.size() << std::endl; } How to do the same thing in Microsoft Visual C++? Is there some way to write this code that works in both GNU C++ and Visual C++?

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  • What's the simplest way of defining lexicographic comparison for elements of a class?

    - by the_mandrill
    If I have a class that I want to be able to sort (ie support a less-than concept), and it has several data items such that I need to do lexicographic ordering then I need something like this: struct MyData { string surname; string forename; bool operator<(const MyData& other) const { return surname < other.surname || (surname==other.surname && forename < other.forename); } }; This becomes pretty unmanageable for anything with more than 2 data members. Are there any simpler ways of achieving it? The data members may be any Comparable class.

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  • Is there a TextWriter interface to the System.Diagnostics.Debug class?

    - by John Källén
    I'm often frustrated by the System.Diagnostics.Debug.Write/WriteLine methods. I would like to use the Write/WriteLine methods familiar from the TextWriter class, so I often write Debug.WriteLine("# entries {0} for connection {1}", countOfEntries, connection); which causes a compiler error. I end up writing Debug.WriteLine(string.Format("# entries {0} for connection {1}", countOfEntries, connection)); which is really awkward. Does the CLR have a class deriving from TextWriter that "wraps" System.Debug, or should I roll my own?

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  • How to address thread-safety of service data used for maintaining static local variables in C++?

    - by sharptooth
    Consider the following scenario. We have a C++ function with a static local variable: void function() { static int variable = obtain(); //blahblablah } the function needs to be called from multiple threads concurrently, so we add a critical section to avoid concurrent access to the static local: void functionThreadSafe() { CriticalSectionLockClass lock( criticalSection ); static int variable = obtain(); //blahblablah } but will this be enough? I mean there's some magic that makes the variable being initialized no more than once. So there's some service data maintained by the runtime that indicates whether each static local has already been initialized. Will the critical section in the above code protect that service data as well? Is any extra protection required for this scenario?

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  • Variables Expired before Asp.net Membership provider automatically logout .

    - by Bendar
    I have a microsoft membership provider. in my application I'm using the variable which saving in cookie (tried session). The problem what I have: my variable expired before a authentication automatically logout. How can I set the time of membership provider automatic logout and expiring variable after 30 mins for example. Or how can I create a new server variable? Or maybe you suggest me better approach? Thank you

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  • What is the purpose of Process class in Java?

    - by Nitesh Panchal
    Runtime objRuntime = Runtime.getRuntime(); String strBackupString = "mysqldump -u " + userName + " -p" + password + " " + dbName; Process objProcess = objRuntime.exec(strBackupString); This is used for backup of database. But what exactly happens? Can anybody make me explain, what is the purpose of Runtime and Process class? Is this class used to act as if we are typing command from command prompt? Then what should i pass to objRuntime.exec() if i want to open notepad? And is the command executed as soon as we call exec method? If yes, then what purpose does Process serve here? I really can't understand these two classes. Please make me understand. Thanks in advance :)

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  • Multiple inclusion of header file c++

    - by iSight
    Hi, I have a problem regarding multiple inclusion of header file in C++ code. say for example, i have three class X,Y,Z. X and Y are derived from Base class Z. And i want to create an instance of X in Y. The code will go like this. class Z{some code} class X:public Z{some code};//here #include header of class Z added class Y:public Z //here #include header of class Z added as well as of X class {private: X* mX;//instance of X some code}; So in this multiple definition of all methods of base class arises. how can i cope with this problem

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  • How do you keep the value of global variables (namely a struct variable) between postbacks?

    - by user3702304
    I'm new to this and have already searched for this with not much luck :( Lets say I have defined a struct array globally and filled the array with data on an Ajax ModalPopupExtender. I then have a ddl_SelectedIndexChanged event that does a postback and seems to recycle my array. Is there a way to fire the ddl_SelectedIndexChanged event to perform some code without doing a postback? Or is there an easy way to make the array of type struct retain it's values? (I am creating a website btw) Thanks in advance...

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  • Is there a method to retrieve the file name of a class?

    - by Dran Dane
    Hello Is there a method to retrieve the file name of a class? Specifically I would like to create a static method (CreateLink) in a base class (BasePage) to automatically return the path and filename of the page called. I code in .C# ASP.NET private const string TEMPLATE = "~/One.aspx"; public static HyperLink CreateLink() { HyperLink link = new HyperLink(); link.Text = "Click here"; link.NavigateUrl = String.Format(TEMPLATE); return link; } Is it possible to avoid the use of TEMPLATE hardcoded variable? Is it possible to retrieve the One.aspx path from file name and location?

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  • What's the most performance effective way to have a webbrowser inside a class library ?

    - by Xaqron
    I'm developing a class library. Need some data from internet and this cannot be done with HttpWebRequest in my case so I wanna use WebBrowser component. WebBrowser is used for opening a single page and fetch some data from it, so WebBrowser life-time is very short. Running thread is MTA and no message pump or STA thread is available by default (class library is used by an ASP.NET application). How to create a WebBrowser object, run it with a STA thread, fetch data from a web page and finally dispose it with the least performance impact on the application ? I just need the idea/concept and will find details myself. Thanks guys

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  • .Net Compact Framework - is there any way in the SerialPort class to set the RTS control to TOGGLE ?

    - by egapotz
    Hi, I found very annoying the fact that the SerialPort class in the .NET Framework doesn't allow to set the rts control to TOGGLE. There is a property called RTSEnable that lets me control directly the status of the RTS signal, but in a Compact Framework app there is not much precision to make it work well. Another solution can be to write a class that calls unmanaged APIs and set the rts control via the DCB structure, but I don't like it since I am using some external libraries that need to reference to a SerialPort instance. Have you any other idea ? Thanks !

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  • Why is the destructor of the class called twice ?

    - by dicaprio
    Apologies if the question sounds silly, I was following experts in SO and trying some examples myself, and this is one of them. I did try the search option but didn't find an answer for this kind. class A { public: A(){cout<<"A Contruction"<<endl;} ~A(){cout<<"A destruction"<<endl;} }; int main() { vector<A> t; t.push_back(A()); // After this line, when the scope of the object is lost. } Why is the destructor of the class called twice ?

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  • C# Why does calling an interface member from a class generate an error?

    - by Jack
    So I have an interface: interface IFoo { int Bar(); int this[int i] {get; set;} } And a class that derives from it class Foo : IFoo { public int IFoo.Bar() { //Implementation { public int IFoo.this[int i] { //Implementation } } Now, I try to do this: var fooey = new Foo(); int i = Fooey.Bar(); or this: int i = Fooey[4]; I would expect these to work properly. However, the compiler generates an error as if such members don't exist. Why is that? I am aware I can cast Foo as IFoo, but I am also aware that casting is costly to performance, which is often the reason to use interfaces in the first place. EDIT 1: These are the errors generated 'Foo' does not contain a definition for 'Bar' and no extension method 'Bar' accepting a first argument of type 'Foo' could be found (are you missing a using directive or an assembly reference?) "Cannot apply indexing to an expression of type 'Foo'"

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  • Java - ClassNotFoundException I have the class included, but why do I get an exception?

    - by aloh
    public static Reservation[] openBinaryFile( String fileName ) { Reservation [] objArray = null; try { ObjectInputStream inStream = new ObjectInputStream( new FileInputStream( fileName ) ); objArray = (Reservation[])inStream.readObject(); inStream.close(); } catch( ClassNotFoundException e ) { System.out.println( "Exception: ClassNotFoundException." ); } I have the class included, but why do I get an exception? The class is in the same package as the others. Why am I getting this exception?

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  • Java inheritance question

    - by user247866
    So I have 3 classes. Abstract class A Class B extends class A independent Class C In class D that contains the main method, I create a list of instances of class B List<B> b = method-call();` // the method returns a list of instances of class B Now in class C I have one method that is common to both A and B, and hence I don't want to duplicate it. I want to have one method that takes as input an instance of class A, as follows: public void some-method(LIst<A> a) However, when I do: C c = new C(). c. some-method(b) I get an error that some-method is not applicable for the argument List, instead it's expecting to get List. Is there a good way to fix this problem? Many thanks!

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  • why can not see my method if i implamented interface to normal class?

    - by Phsika
    i can not see MyLoad.TreeLoader(.... but why i can not see? i implemented iloader to TreeViewLoad. i should see TreeLoader why? namespace Rekursive { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { //treeView1.Nodes.Add("Test"); iloader MyLoad = new TreeViewLoad(); MyLoad.loader("test", treeView1, 1); // i can not see MyLoad.TreeLoader(.... but why i can not see? // i implemented iloader to TreeViewLoad. i should see TreeLoader why? //TreeViewLoad myloader = new TreeViewLoad(); } } interface iloader { void loader(string nodeName, TreeView myTre, int id); } class TreeViewLoad : iloader { public void TreeLoader(TreeView tre) { // i will call loader... } public void loader(string nodeName, TreeView myTre, int id) { myTre.Nodes.Add(nodeName + id.ToString()); if (id

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  • How do I select a class element based on its id in jQuery?

    - by Michael
    I have multiple dynamically generated buttons with a class name of ".button". Each of these are given an unknown ID value used to uniquely identify them. In jQuery I must select one and alert the values. <div class="button" id="3"></div> The ID value is dynamically generated, therefore I do not know it. I'm new to jQuery but am basically looking for something like this: $(".button").attr("id").val(); How do I target one button when there are many? Thanks!

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  • .Htaccess & Wildcard Subdomains — Can't get other variables to work!

    - by Justin Scheetz
    It would be absolutely awesome if someone could help me out here. I have a domain, let's call it "example.com". I have wildcard subdomains setup and working great. The only problem is I can't get htaccess to see anything else like subdomain.example.com/profile/some_name/some_id_number/. In fact, I can type any garbage after the domain and it will still just show me the home screen. Here's what's in my htaccess file now: Options +FollowSymLinks Options +Indexes Options -Multiviews RewriteEngine On RewriteCond %{REQUEST_URI} !^/app/index.php RewriteCond %{HTTP_HOST} !^www\.example\.com RewriteCond %{HTTP_HOST} ^([^.]+)\.example\.com RewriteRule (.*) /app/index.php?user%1 [L] I can see why that wouldn't work yet, but I wanted to add something similar to the following: RewriteRule ^profile/([^/]+)/([^/]+) /app/index.php?page=profile&username=$1&user_id=$2 [nc] But it's not working at all. The server doesn't even really show signs that it's even seeing it there. Any ideas?

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