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  • simple c++ file opening issue

    - by Robert
    #include <iostream> #include <fstream> using namespace std; int main () { ofstream testfile; testfile.open ("test.txt"); testfile << "success!\n"; testfile.close(); return 0; } 1)called "g++ testfile.cpp" 2)created "test.txt" 3)called "chmod u+x a.out" 4)??? 5)file remains blank. I feel like an idiot for failing at something as trivial as this is supposed to be.

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  • Using popen() to invoke a shell command?

    - by Anvar
    When running the following code through xcode I get inconsistent behavior. Sometimes it prints the git version correctly, other times it doesn't print anything. The return code from the shell command is always 0 though. Any ideas on why this might be? What am I doing wrong? #define BUFFER_SIZE 256 int main (int argc, const char * argv[]) { FILE *fpipe; char *command="/opt/local/bin/git --version"; char line[BUFFER_SIZE]; if ( !(fpipe = (FILE*)popen(command, "r")) ) { // If fpipe is NULL perror("Problems with pipe"); exit(1); } while ( fgets( line, sizeof(char) * BUFFER_SIZE, fpipe)) { // Inconsistent (happens sometimes) printf("READING LINE"); printf("%s", line); } int status = pclose(fpipe); if (status != 0) { // Never happens printf("Strange error code: %d", status); } return 0; }

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  • Eclipse bug? Switching on a null with only default case

    - by polygenelubricants
    I was experimenting with enum, and I found that the following compiles and runs fine on Eclipse (Build id: 20090920-1017, not sure exact compiler version): public class SwitchingOnAnull { enum X { ,; } public static void main(String[] args) { X x = null; switch(x) { default: System.out.println("Hello world!"); } } } When compiled and run with Eclipse, this prints "Hello world!" and exits normally. With the javac compiler, this throws a NullPointerException as expected. So is there a bug in Eclipse Java compiler?

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  • Problem while redirecting user after registration

    - by Eternal Learner
    I am creating a simple website . My situation is like this. After registering an user, I want to redirect the user after say 3 seconds to a main page(if the registration succeeds) . The code I have now is as below $query = "INSERT INTO Privileges VALUES('$user','$password1','$role')"; $result = mysql_query($query, $dbcon) or die('Registration Failed: ' . mysql_error()); print 'Thanks for Registering , You will be redirected shortly'; ob_start(); echo "Test"; header("Location: http://www.php.net"); ob_flush() I get the error message Warning: Cannot modify header information - headers already sent by (output started at/home/srinivasa/public_html/ThanksForRegistering.php:27) in /home/srinivasa /public_html/ThanksForRegistering.php on line 35. What do I need to do now ?

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  • Trying to understand Java RSA key size

    - by Tom Brito
    The key generator was initilized with a size of 1024, so why the printed sizes are 635 and 162? import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.NoSuchAlgorithmException; import java.security.NoSuchProviderException; import java.security.interfaces.RSAPrivateKey; import java.security.interfaces.RSAPublicKey; public class TEST { public static KeyPair generateKeyPair() throws NoSuchAlgorithmException, NoSuchProviderException { KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA", "BC"); keyPairGenerator.initialize(1024); return keyPairGenerator.generateKeyPair(); } public static void main(String[] args) throws Exception { KeyPair keyPair = generateKeyPair(); RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); System.out.println("Size = " + privateKey.getEncoded().length); System.out.println("Size = " + publicKey.getEncoded().length); } }

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  • Copy Constructor in C++

    - by user265260
    i have this code #include <iostream> using namespace std; class Test{ public: int a; Test(int i=0):a(i){} ~Test(){ cout << a << endl; } Test(const Test &){ cout << "copy" << endl; } void operator=(const Test &){ cout << "=" << endl; } Test operator+(Test& p){ Test res(a+p.a); return res; } }; int main (int argc, char const *argv[]){ Test t1(10), t2(20); Test t3=t1+t2; return 0; } Output: 30 20 10 Why isnt the copy constructor called here?

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  • Best practices for packaging resources (jpg's, sound, video) in an iPhone app?

    - by Mel
    I'm a newb iPhone developer writing an app that has several large JPGs and sound files. Everything works ok if I drag these non-code resources into my project. But I am wondering if this is the right way to package my app. In Windows development, I would create a "resource DLL" that keeps the .exe size small. What is the equivalent for iPhone? I think I should be creating a "bundle" - can someone please give me some pointers to using these and how to link them into my main project? Thanks!

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  • Android Timer update UI between multiple tasks

    - by Rilcon42
    I have tried multiple ways to have a single persistent timer update the ui in multiple activities, and nothing seems to work. I have tried an AsyncTask, a Handler, and a CountDownTimer. The code below does not execute the first Log.i statement.... Is there a better way to start the timer (which must be called from another class) in Main (which is the only persistent class)? public static void MainLawTimer() { MainActivity.lawTimer = new CountDownTimer(MainActivity.timeLeft, 1000) { public void onTick(long millisUntilFinished) { Log.i("aaa","Timer running. Time left: "+MainActivity.timeLeft); MainActivity.timeLeft--; if(MainActivity.timeLeft<=0) { //do stuff } else { //call method in another class } }

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  • C# compiler fails to recognize a class is implementing an interface

    - by Freek
    The following code fails to compile (using VS2010) and I don't see why. The compiler should be able to infer that List is 'compatible' (sorry for lack of a better word) with IEnumerable, but somehow it doesn't. What am I missing here? interface ITest { void Test(); } class TestClass : ITest { public void Test() { } } class Program { static void Test(IEnumerable<ITest> tests) { foreach(var t in tests) { Console.WriteLine(t); } } static void Main(string[] args) { var lst = new List<TestClass>(); Test(lst); // fails, why? Test(lst.Select(t=>t as ITest)); //success Test(lst.ToArray()); // success } }

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  • DataTemplate / ContentTemplate - exchange controls

    - by Scott Olson
    How can i solve the following (simplified) problem? M-V-VM context. I want to show text at the UI. In case the user has the rights to change the text, i want to use a textbox to manipulate the text. In case the user has no rights, i want to use a label to only show the text. My main problem: how to exchange textbox and label and bind Text resp. Content to the same property in viewmodel. Thanks for your answers Toni

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  • Problem with Initializing Consts

    - by UdiM
    This code, when compiled in xlC 8.0 (on AIX 6.1), produces the wrong result. It should print 12345, but instead prints 804399880. Removing the const in front of result makes the code work correctly. Where is the bug? #include <stdio.h> #include <stdlib.h> #include <string> long int foo(std::string input) { return strtol(input.c_str(), NULL, 0); } void bar() { const long int result = foo("12345"); printf("%u\n", result); } int main() { bar(); return 0; } Compilation command: /usr/vacpp/bin/xlC example.cpp -g

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  • Javascript - use to load xml data from URL

    - by spenf
    I have this url with some xml data in it: http://64.182.231.116/~spencerf/union_college/Upperclass_Sample_Menu.xml And I would like to load this xml data into my javascript script so I can parse it. I am using parse.com Javascript SDK, in there cloud code. Here is the code I have tried: Parse.Cloud.define("next", function(request, response) { response.success("Hello world!"); $.ajax({ url: 'http://64.182.231.116/~spencerf/union_college/Upperclass_Sample_Menu.xml', // name of file you want to parse dataType: "xml", // type of file you are trying to read success: parse, // name of the function to call upon success error: function(){alert("Error: Something went wrong");} }); }); But when I run this I get an error: $ is not defined at main.js:

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  • Large amount of constants in Java

    - by Lars D
    I need to include about 1 MByte of data in a Java application, for very fast and easy access in the rest of the source code. My main background is not Java, so my initial idea was to convert the data directly to Java source code, defining 1MByte of constant arrays, classes (instead of C++ struct) etc., something like this: public final/immutable/const MyClass MyList[] = { { 23012, 22, "Hamburger"} , { 28375, 123, "Kieler"} }; However, it seems that Java does not support such constructs. Is this correct? If yes, what is the best solution to this problem?

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  • Change list link to foreign key change page

    - by Adam
    When viewing the admin change list for a model, is it possible to make the columns that correspond to foreign keys links to their respective pages? A simple example is I have a Foo object which contains Bar as a foreign key. If I'm viewing the admin change list for Foo (and have it set to include Bar in the display_list columns), the main column would link to the Foo instance's edit page while the Bar column would link to the Boo instance's edit page. I understand I can override the template that's used, but I was curious if there was a solution that didn't require that.

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  • java multiple connections between server and one client

    - by user1507128
    I'm trying to make like a skype-instant messager, my idea for it is to have one server which handles multiple connections for the clients. What I now have is a friend list etc, but now I want to create Threads both for server and client to handle a conversation. The problem is that I need multiple connections between a server and one client for every conversation(I think). but i dont think it's possible. Does someone have another way for doing this or maybe a way to make multiple connections between the server and a client? Thanks for helping me out PS: English is not my main language so please excuse me for my grammar.

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  • .htaccess rewrite issue with P

    - by Cyclone
    This is a followup for this question. When I used the proxy flag, I did not know all of its effects. Now I have two more problems, which need to be fixed! The main problem is with user IP addresses, everyone appears to use the server IP. I can't trust http-x-forwarded-for because it is easy to forge headers, and the REMOTE_ADDR just shows the server IP. I used the P flag because it acted as a mask, but Google loads everything with the actual URL. How can I use this subdomain rewrite without the P flag? It needs to be internal. Thank you for your help!

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  • Django date filter: how come the format used is different from the one in datetime library?

    - by sebpiq
    For formatting a date using date filter you must use the following format : {{ my_date|date:"Y-m-d" }} If you use strftime from the standard datetime, you have to use the following : my_date.strftime("%Y-%m-%d") So my question is ... isn't it ugly (I guess it is because of the % that is used also for tags, and therefore is escaped or something) ? But that's not the main question ... I would like to use the same DATE_FORMAT parametrized in settings.py all over the project, but it therefore seems that I cannot ! Is there a work around (for example a filter that removes the % after the date has been formatted like {{ my_date|date|dream_filter }}, because if I just use DATE_FORMAT = "%Y-%m-%d" I got something like %2001-%6-%12)?

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  • How can I close the currently running server app when I launch new debug session?

    - by Eonil
    Google App Engine (GAE) Java SDK uses eclipse as main IDE. IDE runs a server app when I launch debugging session. And it runs another server app when I launch debugging session again. It closes the server app when I stop the debugging session, but it doesn't when I re-launch debugging session. Re-launching means stop and launch again. Why does it stop existing app? So I have to close the server app manually at each time. Is there a way to close existing running app when re-launching debugging session?

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  • Why do C# and Java require everything to be in a class?

    - by Javier Badia
    It seemed like this question should have been asked before, but searching found nothing. I've always wondered what's the point of making us put every bit of code inside a class or interface. I seem to remember that there were some advantages to requiring a main() function like C, but nothing for classes. Languages like Python are, in a way, even more object oriented than Java since they don't have primitives, but you can put code wherever you want. Is this some sort of "misinterpretation" of OOP? After all, you can write procedural code like you would in C and put it inside a class, but it won't be object oriented.

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  • How does the below program work in c++?

    - by Srinivasa Varadan
    I have just created 2 pointers which has undefined behavior and try to invoke a class member function which has no object created ? I don't understand this? #include<iostream> using namespace std; class Animal { public: void talk() { cout<<"I am an animal"<<endl; } }; class Dog : public Animal { public: void talk() { cout<<"bark"<<endl; } }; int main() { Animal * a; Dog * d; d->talk(); a->talk(); }

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  • Why is this C or C++ macro not expanded by the preprocessor?

    - by Atul
    Can someone points me the problem in the code when compiled with gcc 4.1.0. #define X 10 int main() { double a = 1e-X; return 0; } I am getting error:Exponent has no digits. When i replace X with 10, it works fine. Also i checked with g++ -E command to see the file with preprocessors applied, it has not replaced X with 10. I was under the impression that preprocessor replaces every macro defined in the file with the replacement text with applying any intelligence. Am I wrong? I know this is a really silly question but I am confused and I would rather be silly than confused :). Any comments/suggestions.

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  • Difficulty understanding behavior of free()

    - by Rasmi Ranjan Nayak
    int main() { int *ptr, **ptr1; ptr = (int*)malloc(sizeof(int)); ptr1 = (int**)malloc(sizeof(int)); free(ptr); *ptr = 12345; ptr1 = &ptr; //free(ptr); //**ptr1 = 23456; printf("%d \n", **ptr1); system("pause"); return 0; } How does *ptr store the value 12345, when the memory has already been freed? So, now ptr should be pointing to garbage. Why is this happening?

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  • C++ code visualization

    - by bobobobo
    A sort of follow up/related question to this. I'm trying to get a grip on a large code base that has hundreds and hundreds of classes and a large inheritance hierarchy. I want to be able to see the "main veins" of the inheritance hierarchy at a glance - not all the "peripheral" classes that only do some very specific / specialized thing. Visual Studio's "View Class Diagram" makes something that looks like a train and its sprawled horizontally across the screen and isn't very organized. You can't grok it easily. I've just tried doxygen and graphviz but the results are .. somewhat similar to Visual Studio. I'm getting sweet looking call graphs but again too much detail for what I'm trying to get. I need a quick way to generate the inheritance hierarchy, in some kind of collapsible view.

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  • C++ - How to call a member function for an inherited object.

    - by Francisco P.
    Hello! I have a few classes (heat, gas, contact, pressure) inheriting from a main one (sensor). I have a need to store them in a vector<Sensor *> (part of the specification). At some point in time, I need to call a function that indiscriminately stores those Sensor *. (also part of the specification, not open for discussion) Something like this: for(size_t i = 0; i < Sensors.size(); ++i) Sensors[i]->storeSensor(os) //os is an ofstream kind of object, passed onwards by reference Where and how shall storeSensor be defined? Is there any simple way to do this or will I need to disregard the specification? Mind you, I'm a beginner! Thanks for your time!

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  • how to get stl map to construct/destruct inserted object only once.

    - by Alberto Toglia
    I have found a very prejudicial fact about stl maps. For some reason I cant get objects being inserted in the map to get constructed/destructed only once. Example: struct MyObject{ MyObject(){ cout << "constructor" << endl; } ~MyObject(){ cout << "destructor" << endl; } }; int main() { std::map<int, MyObject> myObjectsMap; myObjectsMap[0] = MyObject(); return 0; } returns: constructor destructor destructor constructor destructor If I do: typedef std::pair<int, MyObject> MyObjectPair; myObjectsMap.insert( MyObjectPair(0,MyObject())); returns: constructor destructor destructor destructor I'm inserting Objects responsible for their own memory allocation, so when destructed they'll clean themselves up, being destructed several times is causing me some trouble.

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