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  • Calling a method on an object a bunch of times versus constructing an object a bunch of times

    - by Ami
    I have a List called myData and I want to apply a particular method (someFunction) to every element in the List. Is calling a method through an object's constructor slower than calling the same method many times for one particular object instantiation? In other words, is this: for(int i = 0; i < myData.Count; i++) myClass someObject = new myClass(myData[i]); slower than this: myClass someObject = new myClass(); for(int i = 0; i < myData.Count; i++) someObject.someFunction(myData[i]); ? If so, how much slower?

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  • doubt in - Function Objects - c++

    - by Eternal Learner
    I have a class class fobj{ public: fobj(int i):id(i) {} void operator()() { std::cout<<"Prints"<<std::endl; } private: int id; }; template<typename T> void func(T type) { type(); } My Doubt is if I invoke func like Method 1: func(fobj(1); the message I wanted to print is printed. I was always thinking I needed to do something like Method 2: fobj Iobj(1); // create an instance of the fobj class func(Iobj); //call func by passing Iobj(which is a function object) How does Method 1 work? I mean what exactly happens? and how is a call made to the operator() in class fobj ?

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  • Method sscanf() ambiguous behavior

    - by Carmen Cojocaru
    I am trying to understand how sscanf() works. I ran some examples from this page: http://docs.roxen.com/pike/7.0/tutorial/strings/sscanf.xml and they don't work on my platform. I can't understand why. For instance: "sscanf("4711bar", "%d%s", a, b);" makes the program exit with an error... Here is one of the examples that work: "sscanf("foo", "f%s", a);". Does anybody know why? Do they work on your platforms? Thank you. This is my code: int main(void){ char *b = (char*)malloc(sizeof(char)*100); int a = 0; sscanf("4711bar", "%d%s", a, b); printf("%d", a); printf("%s", b); }

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  • How to use Externel Procedures in Triggers on Oracle 11g..

    - by RBA
    Hi, I want to fire a trigger whenever an insert command is fired.. The trigger will access a pl/sql file which can change anytime.. So the query is, if we design the trigger, how can we make sure this dynamic thing happens.. As during the stored procedure, it is not workingg.. I think - it should work for 1) External Procedures 2) Execute Statement Please correct me, if I am wrong.. I was working on External Procedures but i am not able to find the way to execute the external procedure from here on.. SQL> CREATE OR REPLACE FUNCTION Plstojavafac_func (N NUMBER) RETURN NUMBER AS 2 LANGUAGE JAVA 3 NAME 'Factorial.J_calcFactorial(int) return int'; 4 / @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ SQL> CREATE OR REPLACE TRIGGER student_after_insert 2 AFTER INSERT 3 ON student 4 FOR EACH ROW How to call the procedure from heree... And does my interpretations are right,, plz suggest.. Thanks.

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  • When should we use * and & and . and -> ?

    - by uzay95
    Why we are using * character when we are creating button but we aren't adding it to app instance? #include <QApplication> #include <QPushButton> int main(int argc,char *argv[]) { QApplication app(argc,argv); QPushButton *button = new QPushButton("Button Text"); QObject::connect(button,SIGNAL(clicked()),&app,SLOT(quit())); button->show(); return app.exec(); } When should we use * and & and . and - ?

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  • OpenCV (c++) multi channel element access

    - by Vic
    I'm trying to use the "new" 2.0 c++ version of OpenCV, but everything is else like in simple C version. I have some problem with changing the values in image. The image is CV_8UC3. for (int i=0; i<image.rows; i++) { for (int j=0; j<image.cols; j++) { if (someArray[i][j] == 0) { image.at<Vec3i>(i,j)[0] = 0; image.at<Vec3i>(i,j)[1] = 0; image.at<Vec3i>(i,j)[2] = 0; } } } It's not working. What am I doing wrong??? Thank you!

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  • Why does this static factory method involving implied generic types, work?

    - by Cheeso
    Consider public class Tuple<T1, T2> { public Tuple(T1 v1, T2 v2) { V1 = v1; V2 = v2; } public T1 V1 { get; set; } public T2 V2 { get; set; } } public static class Tuple { // MAGIC!! public static Tuple<T1, T2> New<T1, T2>(T1 v1, T2 v2) { return new Tuple<T1, T2>(v1, v2); } } Why does the part labeled "MAGIC" in the above work? It allows syntax like Tuple.New(1, "2") instead of new Tuple<int, string>(1, "2"), but ... how and why? Why do I not need Tuple.New<int,string>(1, "2") ??

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  • Loading Unmanaged C++ in C#. Error Attempted to read or write protected memory

    - by Thatoneguy
    I have a C++ function that looks like this __declspec(dllexport) int ___stdcall RegisterPerson(char const * const szName) { std::string copyName( szName ); // Assign name to a google protocol buffer object // Psuedo code follows.. Protobuf::Person person; person->set_name(copyName); // Error Occurs here... std::cerr << person->DebugString() << std::endl; } The corresponding C# code looks like this... [DllImport(@"MyLibrary.dll", SetLastError = true)] public static unsafe extern int RegisterPerson([MarshalAs(UnmanagedType.LPTStr)]string szName) Not sure why this is not working. My C++ library is compiled as Multi Threaded DLL with MultiByte encoding. Any help would be appreciated. I saw this is a common problem online but no answers lead me to a solution for my problem.

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  • MySQL Integer vs DateTime index

    - by David Kuridža
    Let me start by saying I have looked at many similar questions asked, but all of them relate to Timestamp and DateTime field type without indexing. At least that is my understanding. As we all know, there are certain advantages when it comes to DateTime. Putting them aside for a minute, and assuming table's engine is InnoDB with 10+ million records, which query would perform faster when criteria is based on: DateTime with index int with index In other words, it is better to store date and time as DateTime or UNIX timestamp in int? Keep in mind there is no need for any built-in MySQL functions to be used.

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  • TSQL Prefixing String Literal on Insert - Any Value to This, or Redundant?

    - by SethO
    I just inherited a project that has code similar to the following (rather simple) example: DECLARE @Demo TABLE ( Quantity INT, Symbol NVARCHAR(10) ) INSERT INTO @Demo (Quantity, Symbol) SELECT 127, N'IBM' My interest is with the N before the string literal. I understand that the prefix N is to specify encoding (in this case, Unicode). But since the select is just for inserting into a field that is clearly already Unicode, wouldn't this value be automatically upcast? I've run the code without the N and it appears to work, but am I missing something that the previous programmer intended? Or was the N an oversight on his/her part? I expect behavior similar to when I pass an int to a decimal field (auto-upcast). Can I get rid of those Ns?

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  • Multiple Linked List in C

    - by LuckySlevin
    I have a problem about Linked Lists. I already know how to create structures and linked list. But now I have to create arbitrary number of linked list which are also be kept in another structure. Which means : struct list{int x, struct list *next; }; struct parent{int x, struct list *head, struct parent *next;} And after lists are created when i enter this input for example "123134 linked list should look like : 1 - 2 - 3 - 4 And for example 1 will contain 2-3 list inside of it, 3 will contain 1-4 list inside of it. I need a starting point and a spark from you. So how can i do this?

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  • C++ stringstream reads all zero's

    - by user69514
    I have a file which contains three integers per line. When I read the line I use a stringstream to separate the values, but it only reads the first value as it is. The other two are read as zero's. ifstream inputstream(filename.c_str()); if( inputstream.is_open() ){ string line; stringstream ss; while( getline(inputstream, line) ){ //check line and extract elements int id; double income; int members; ss.clear(); ss.str(line); ss >> id >> income >> members; In the case above, id is extracted correctly, but income, and members get assigned zero instead of the actual value.

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  • Why can't I reserve 1,000,000,000 in my vector ?

    - by vipersnake005
    When I type in the foll. code, I get the output as 1073741823. #include <iostream> #include <vector> using namespace std; int main() { vector <int> v; cout<<v.max_size(); return 0; } However when I try to resize the vector to 1,000,000,000, by v.resize(1000000000); the program stops executing. How can I enable the program to allocate the required memory, when it seems that it should be able to? I am using MinGW in Windows 7. I have 2 GB RAM. Should it not be possible? In case it is not possible, can't I declare it as an array of integers and get away? BUt even that doesn't work. Another thing is that, suppose I would use a file(which can easily handle so much data ). How can I let it read and write and the same time. Using fstream file("file.txt', ios::out | ios::in ); doesn't create a file, in the first place. But supposing the file exists, I am unable to use to do reading and writing simultaneously. WHat I mean is this : Let the contents of the file be 111111 Then if I run : - #include <fstream> #include <iostream> using namespace std; int main() { fstream file("file.txt",ios:in|ios::out); char x; while( file>>x) { file<<'0'; } return 0; } Shouldn't the file's contents now be 101010 ? Read one character and then overwrite the next one with 0 ? Or incase the entire contents were read at once into some buffer, should there not be atleast one 0 in the file ? 1111110 ? But the contents remain unaltered. Please explain. Thank you.

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  • [C++] Run codes for only 60 times each second.

    - by djzmo
    Hello there, I'm creating a directx application that relies on the system time (because it must be accurate), and I need to run lines of code for 60 times each second in the background (in a thread created by boost::thread). that's equal to 60 FPS (frame per second), but without depending on the main application frame rate. //................. void frameThread() { // I want to run codes inside this loop for *exactly* 60 times in a second. // In other words, every 16.67 (1000/60) milliseconds for(;;) { DoWork(); //......... } } int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) { initialize(); //.....stuffs boost::thread framethread(frameThread); //...... } Is there a way to do this? Any kind of help would be appreciated :)

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  • C++: Throwing shared_ptr of derived and catching shared_ptr of base?

    - by hasvn
    Ok, I've been told this problem: Why can you throw a pointer to a derived class and catch a pointer to its base... but you can't do that with shared_ptrs? Example, this works: class Base {}; class Derived : public Base {}; int main() { try { throw new Derived() ; } catch( const Base2 * b ) { printf("Received a base" ) ; } return 0 ; } But this doesn't int main() { try { throw std::tr1::shared_ptr<Derived>( new Derived() ) ; } catch( const std::tr1::shared_ptr<Base> & b ) { printf("Received a base" ) ; } return 0 ; } Any ideas?

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  • Count The Amount Of Data In An Array Including SOME Null

    - by Josephine
    I'm coding in java and I need to create a function that returns the number of Data objects that are currently in an ArrayList. At the moment I have this: int count = 0; for (int i = 0; i < data.length; i++) { if (data[i] != null) { count ++; } } return count; But the problem is that an array list that includes null data is acceptable, and I have to count their null data towards this counter. How do I include the null data that's in the middle of this array, and not the null data that's not supposed to be counted for? For example, I have some tester code that adds (8),null,null,(23),(25) to the array, and this function should return 5 when the initial array size is 10. Thank you so much

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  • Determine an object's class returned by a factory method (Error: function does not take 1 arguments

    - by tzippy
    I have a factorymethod that either returns an object of baseclass or one that is of derivedclass (a derived class of baseclass). The derived class has a method virtual void foo(int x) that takes one argument. baseclass however has virtual void foo() without an argument. In my code, a factory method returns a pointer of type bar that definetly points to an object of class derivedclass. However since this is only known at runtime I get a compiler error saying that foo() does not take an argument. Can I cast this pointer to a pointer of type derivedclass? std::auto_ptr<baseclass> bar = classfactory::CreateBar(); //returns object of class derivedclass bar->foo(5); class baseclass { public: virtual void foo(); } class derivedclass : public baseclass { public: virtual void foo(int x); }

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  • Explicit constructor still has default values even though a default constructor is not invoked.

    - by Phoenix
    According to my understanding a default constructor initializes the state of the object to default values, so if i provide an explicit no-arg public constructor like this then how are the values of d and e still getting initialized to zero because in this case the default constructor is not invoked. public class B extends A{ private int d; private int e; public B() { System.out.println(d); System.out.println(e); } } EDIT:: The only thing default constructor does is call to super() then how come if i have a explicitly mentioned a constructor here and A has a protected variable say c which is initialized to 17 in its constructor. Should I not be explicitly calling super() to be able to see that change since I'm using my own constructor ? Why is B still getting the value of 17 through inheritance ?

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  • i have done code so please help

    - by davit-datuashvili
    public class bitap{ public static void main(String[]args){ String text="tbillisi"; String pattern="tbilxiri"; int k=2; int m=pattern.length(); long pattern_mask[]=new long[Character.MAX_VALUE+1]; String result=""; boolean[]R=new boolean[m+1]; long i,d; for (i=0;i<=k;i++){ R[i]=~1; } for (i=0;i if (0==(R[k]& (1< System.out.println(result); } } http://en.wikipedia.org/wiki/Bitap_algorithm from this site

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  • which type is best for three radiobuttons?

    - by Manog
    Maybe you consider this question trivial but im just curious what is your opinion. I have three radiobuttons. "Show blue", "Show red" and "Show all". I did it with nullable boolean. There is collumn in database where blue is 0 and red is 1 so in metode i have to translate bool to int to compare those values (i do it in c#).Of course it works, but i wonder if it is the best solution. And question is wich type is best in this case? nullable bool, int, or maybe string?

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  • activating the class need help.... :)

    - by asm_debuger
    this is my code... i dont anderstend way the class dont work... import java.awt.BorderLayout; import java.awt.Button; import java.awt.Color; import java.awt.GridLayout; import java.awt.Panel; public class Caldesinger { public Panel p1=new Panel(); public Button[] arr=new Button[20]; public String[] name = {"9","8","7","6","5","4","3","2","1","0","+","-","*","/",".","cos","sin","=","pow"}; public Caldesinger() { for (int i = 0; i < arr.length; i++) { this.arr[i]=new Button(""+name[i]); } } public Panel getP1() { return p1; } public void setP1(Panel p1) { this.p1 = p1; } public Button[] getArr() { return arr; } public void setArr(Button[] arr) { this.arr = arr; } public Object c() { this.p1.setLayout(new GridLayout(4,15)); for (int i = 0; i < arr.length; i++) { arr[i].setBackground(Color.LIGHT_GRAY); arr[i].setForeground(Color.orange); p1.add(arr[i]); } this.p1.setLayout(new GridLayout(4,15)); return this; } } the class desinge the applet this is the main: import java.applet.Applet; import java.awt.BorderLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; public class Mainapp extends Applet implements ActionListener { Caldesinger desinge=new Caldesinger (); public void init() { this.setLayout(new BorderLayout()); this.desinge.c(); } public void ActionPerformed(ActionEvent arg0) { for (int i = 0; i <20; i++) { if(arg0.getSource()== this.desinge.arr[i]); } } } way the method c does not work? the method desinge the applet

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  • Getting input in system() function (Mac)

    - by Alex
    #include <iostream> using namespace std; int main() { short int enterVal; cout << "enter a number to say: " << endl; cin >> enterVal; system("say "%d"") << enterVal; return 0; } Is what I am currently trying. I want the user to enter a number and the system() function says it basically. The code above has an error which says " 'd' was not declared in this scope ". Thanks in advance.

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  • Common type for generic classes of different types

    - by DinGODzilla
    I have (for example) Dictionary of different generic types (d1, d2, d3, d4) and I want to store them in something var d1 = new Dictionary<int, string>(); var d2 = new Dictionary<int, long>(); var d3 = new Dictionary<DateTime, bool>(); var d4 = new Dictionary<string, object>(); var something = ??? //new List<object> {d1, d2, d3, d4}; Is there any other way how to store that in something with common denominator different than object? Thanks :-)

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  • Java Double Array

    - by user1062058
    I'm having trouble setting up and placing values into an array using a text file containing the floating point numbers 2.1 and 4.3 each number is separated by a space - below is the error I'm getting: Exception in thread "main" java.util.NoSuchElementException import java.util.*; import java.io.*; public class DoubleArray { public static void main(String[] args) throws FileNotFoundException { Scanner in = new Scanner(new FileReader("mytestnumbers.txt")); double [] nums = new double[2]; for (int counter=0; counter < 2; counter++) { int index = 0; index++; nums[index] = in.nextDouble(); } } } Thanks, I'm sure this isn't a hard question to answer... I appreciate your time.

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  • Java Collections.Rotate with an array doesn't work

    - by steve_72
    I have the following java code: import java.util.Arrays; import java.util.Collections; public class Test { public static void main(String[] args) { int[] test = {1,2,3,4,5}; Collections.rotate(Arrays.asList(test), -1); for(int i = 0; i < test.length; i++) { System.out.println(test[i]); } } } I want the array to be rotated, but the output I get is 1 2 3 4 5 Why is this? And is there an alternative solution?

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