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  • Distinguish between a single click and a double click in Java

    - by user552279
    Hi, I search the forum and see this codes: public void mouseClicked(MouseEvent e) { if (e.getClickCount() == 2) { System.out.println(" and it's a double click!"); wasDoubleClick = true; } else { Integer timerinterval = (Integer) Toolkit.getDefaultToolkit().getDesktopProperty( "awt.multiClickInterval"); timer = new Timer(timerinterval.intValue(), new ActionListener() { public void actionPerformed(ActionEvent evt) { if (wasDoubleClick) { wasDoubleClick = false; // reset flag } else { System.out.println(" and it's a simple click!"); } } }); timer.setRepeats(false); timer.start(); } } but the code runs incorrectly(Sometime it prints out " and it's a single click!" 2 times . It should print out " and it's a double click!"). Can anybody show me why? or can you give me some better ways to do this? Thank you!

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  • C++ Pointer Issue

    - by Winder
    _stuckVertices is an array of pointers and I would like to update one index of that array without using _stuckVertices[ (row * _cols) + column ] 3 times. The reason it is an array of pointers is because the vast majority of the time the pointer will be NULL. The following code works but I need to dereference a each time I use it: void Cloth::stickPoint(int column, int row) { Anchor **a = &_stuckVertices[ (row * _cols) + column ]; if (!*a) *a = new Anchor(this, column, row); (*a)->stick(); } I originally had it written like this, but the _stuckVertices pointer doesn't get updated: void Cloth::stickPoint(int column, int row) { Anchor *a = _stuckVertices[ (row * _cols) + column ]; if (!a) a = new Anchor(this, column, row); a->stick(); } Is there a way to write Anchor *a = _stuckVertices[ index ] so that a is like an alias into the array that I can update, or is something like the first piece of code how I should do this? Thanks

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  • Dynamic creation of a pointer function in c++

    - by Liberalkid
    I was working on my advanced calculus homework today and we're doing some iteration methods along the lines of newton's method to find solutions to things like x^2=2. It got me thinking that I could write a function that would take two function pointers, one to the function itself and one to the derivative and automate the process. This wouldn't be too challenging, then I started thinking could I have the user input a function and parse that input (yes I can do that). But can I then dynamically create a pointer to a one-variable function in c++. For instance if x^2+x, can I make a function double function(double x){ return x*x+x;} during run-time. Is this remotely feasible, or is it along the lines of self-modifying code?

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  • Why is address zero used for null pointer?

    - by Joel
    In C (or C++ for that matter), pointers are special if they have the value zero: I am adviced to set pointers to zero after freeing their memory, because it means freeing the pointer again isn't dangerous; when I call malloc it returns a pointer with the value zero if it can't get me memory; I use if (p != 0) all the time to make sure passed pointers are valid etc. But since memory addressing starts at 0, isn't 0 just as a valid address as any other? How can 0 be used for handling null pointers if that is the case? Why isn't a negative number null instead?

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  • Freeing a character pointer returns error

    - by Kraffs
    I'm trying to free a character pointer after having used it but it returns a strange error. The error says: "_CrtDbgREport: String too long or IO Error" The debugger itself returns no errors while compiling. The code currently looks like this: void RespondToUser(SOCKET client, SOCKET server) { char buffer[80]; char *temp = malloc(_scprintf("HTTP/1.1 200 OK\r\n%s\r\nServer: %s\r\nConnection: close\r\n\r\nHi!", buffer, SERVER_NAME)); sprintf(temp, "HTTP/1.1 200 OK\r\n%s\r\nServer: %s\r\nConnection: close\r\n\r\nHi!", buffer, SERVER_NAME); send(client, temp, strlen(temp), 0); closesocket(client); free(temp); ListenToUsers(server); } The problem only occurs when I try to free the temp pointer from the memory and not otherwise. What might be causing this?

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  • Problem with pointer copy in C

    - by Stefano Salati
    I radically re-edited the question to explain better my application, as the xample I made up wasn't correct in many ways as you pointed out: I have one pointer to char and I want to copy it to another pointer and then add a NULL character at the end (in my real application, the first string is a const, so I cannot jsut modify it, that's why I need to copy it). I have this function, "MLSLSerialWriteBurst" which I have to fill with some code adapt to my microcontroller. tMLError MLSLSerialWriteBurst( unsigned char slaveAddr, unsigned char registerAddr, unsigned short length, const unsigned char *data ) { unsigned char *tmp_data; tmp_data = data; *(tmp_data+length) = NULL; // this function takes a tmp_data which is a char* terminated with a NULL character ('\0') if(EEPageWrite2(slaveAddr,registerAddr,tmp_data)==0) return ML_SUCCESS; else return ML_ERROR; } I see there's a problem here: tha fact that I do not initialize tmp_data, but I cannot know it's length.

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  • C pointer initialization and dereferencing, what's wrong here?

    - by randombits
    This should be super simple, but I'm not sure why the compiler is complaining here. #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) { int *n = 5; printf ("n: %d", *n); exit(0); } Getting the following complaints: foo.c: In function ‘main’: foo.c:6: warning: initialization makes pointer from integer without a cast I just want to print the value that the pointer n references. I'm dereferencing it in the printf() statement and I get a segmentation fault. Compiling this with gcc -o foo foo.c.

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  • Count double palindromes in given int sequence

    - by jakubmal
    For a given int sequence check number of double palindromes, where by double palindrome we mean sequence of two same palindromes without break between them. So for example: in 1 0 1 1 0 1 we have 1 0 1 as a palindrome which appears 2 times without a break, in 1 0 1 5 1 0 1 we have 1 0 1 but it's separated (apart from the other palindromes in these sequences) Problem example test data is: 3 12 0 1 1 0 0 1 1 0 0 1 1 0 12 1 0 1 0 1 0 1 0 1 0 1 0 6 3 3 3 3 3 3 with answers 8 0 9 Manacher is obvious for the begging, but I'm not sure what to do next. Any ideas appreciated. Complexity should be below n^2 I guess. EDIT: int is here treated as single element of alphabet

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  • double returning only one precision in java

    - by srinath
    in my code i am performing division on numbers and storing it in a double variable. but the variable is returning with only one precision. i want to increase the precision how could i do that. double x; for ( int i =0 ; i<10000 ; i++) { x= w[i] / l[i]; System.out.println(x); } in the above code w and l are integer arrays; i am getting output like 3.0 0.0 1.0 0.0 i want to increase the precision upto 4 atleast.

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  • Set argument pointer to point to new memory inside a function (without returning it) IN C

    - by user321605
    Hello, Hopefully my title was descriptive enough to attract the right help. I want to write a function that will return 1 thing, and modify a provided pointer in another. My current function declaration is . . . char * afterURL replaceURLS(char * body) What I want to do is copy all of body's data into a new string, and set body to point to this new data. I then want afterURL to point to a location within the new string. My issue is getting the actual pointer that is passed in to this function to point to the new data. Thanks in advance! Rob

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  • Null Pointer Exception with an array of bitsets

    - by p0ny
    could someone explain to me why the following results in a Null pointer Exception? And how to set a value for bitarray[0]? BitSet[] bitarray; bitarray= new BitSet[10]; bitarray[0].set(1); Also, why something like this work and not result in a pointer exception? BitSet[] bitarray = new BitSet[10]; BitSet bits = new BitSet(32); bits.set(1); bitarray[0] = bits; 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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  • A pointer member variable having different values

    - by Rohan Prabhu
    Ok, to begin with, this is my code: HyperSprite::HyperSprite() { _view = 0; } void HyperSprite::publish(QGraphicsView* view) { _view = view; } void HyperSprite::getKFrame() { if(_view != 0) { qDebug()<<(void*)_view; } } Now, if I call HyperSprite::getKFrame() from within main(), I get the output: 0xbf8ffb84 I have a TCP server, which requires this QGraphicsView* variable. So whenever a new connection is made, HyperSprite::getKFrame() is called. However, whenever I make a connection to my server, this is the output: 0x1e425ff I honestly don't understand this. Shouldn't the value of a member remain same throughout? Why is the pointer value changing? As is obvious, whenever I try to use the _view pointer to access any of its members, a Segmentation Fault occurs. I tried using QSharedPointer, but it also results in the same problem. The data of the QSharedPointer automatically changes. Why is this happening?

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  • Type casting int into double C++

    - by user1705380
    I am new to programming and this might be an obvious question, though i cannot for life of me figure out why my program is not returning as a double. I am suppose to write a stocks program that takes in shares of stock, whole dollar portion of price and the fraction portion. And the fraction portion is to be inputted as two int values, and include a function definition with 3 int values.The function returns the price as a double. #include <iostream> using namespace std; int price(int, int, int); int main() { int dollars, numerator, denominator, price1, shares; char ans; do { cout<<"Enter the stock price and the number of shares.\n"; cout<<"Enter the price and integers: Dollars, numerator, denominator\n"; cin>>dollars>>numerator>>denominator; cout<<"Enter the number of shares held\n"; cin>>shares; cout<<shares; price1 = price(dollars,numerator,denominator); cout<<" shares of stock with market price of "; cout<< dollars << " " << numerator<<'/'<<denominator<<endl; cout<<"have a value of " << shares * price1<<endl; cout<<"Enter either Y/y to continue"; cin>>ans; }while (ans == 'Y' || ans == 'y'); system("pause"); return 0; } int price(int dollars, int numerator, int denominator) { return dollars + numerator/static_cast<double>(denominator); }

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  • Preserving NULL values in a Double Variable

    - by Sam
    Hi, I'm working on a vb.net application which imports from an Excel spreadsheet. If rdr.HasRows Then Do While rdr.Read() If rdr.GetValue(0).Equals(System.DBNull.Value) Then Return Nothing Else Return rdr.GetValue(0) End If Loop Else I was using string value to store the double values and when preparing the database statement I'd use this code: If (LastDayAverage = Nothing) Then command.Parameters.AddWithValue("@WF_LAST_DAY_TAG", System.DBNull.Value) Else command.Parameters.AddWithValue("@WF_LAST_DAY_TAG", Convert.ToDecimal(LastDayAverage)) End If I now have some data with quite a few decimal places and the data was put into the string variable in scientific notation, so this seems to be the wrong approach. It didn't seem right using the string variable to begin with. If I use a double or decimal type variable, the blank excel values come across as 0.0. How can I preserve the blank values? Thanks

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  • Reading function pointer syntax

    - by bobobobo
    Everytime I look at a C function pointer, my eyes glaze over. I can't read them. From here, here are 2 examples of function pointer TYPEDEFS: typedef int (*AddFunc)(int,int); typedef void (*FunctionFunc)(); Now I'm used to something like: typedef vector<int> VectorOfInts ; Which I read as typedef vector<int> /* as */ VectorOfInts ; But I can't read the above 2 typedefs. The bracketing and the asterisk placement, it's just not logical. Why is the * beside the word AddFunc..?

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  • pointer and malloc [closed]

    - by gcc
    How many methods/ways are there taking input by using with pointer and dynamic memory? Input: 3 1 2 n k l 2 1 2 p 4 55 62 * # x (x is stop value, first input always integer) Example code: p=malloc(sizeof(int)); scanf("%d",&num_arrays); while(1) { scanf("%c",&(*(p+i))); if(*(p+i)=='x') break; ++i; } "3" is stored in num_arrays. The other input values are stored in pointer[array].

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  • How to convert a void pointer to array of classes

    - by user99545
    I am trying to convert a void pointer to an array of classes in a callback function that only supports a void pointer as a means of passing paramaters to the callback. class person { std::string name, age; }; void callback (void *val) { for (int i = 0; i < 9; i++) { std::cout << (person [])val[i].name; } } int main() { person p[10]; callback((void*)p); } My goal is to be able to pass an array of the class person to the callback which then prints out the data such as their name and age. However, the compile does not like what I am doing and complains that error: request for member 'name' in 'val', which is of non-class type 'void*' How can I go about doing this?

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  • how to copy an array into somewhere else in the memory by using the pointer

    - by user2758510
    I am completely new in c++ programming. I want to copy the array called distances into where pointer is pointing to and then I want to print out the resul to see if it is worked or not. this is what I have done: int distances[4][6]={{1,0,0,0,1,0},{1,1,0,0,1,1},{1,0,0,0,0,0},{1,1,0,1,0,0}}; int *ptr; ptr = new int[sizeof(distances[0])]; for(int i=0; i<sizeof(distances[0]); i++){ ptr=distances[i]; ptr++; } I do not know how to print out the contents of the pointer to see how it works.

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  • C++: Checking for non-numeric input and assigning to a double

    - by Brundle
    Here is the code I have at the moment: char ch; int sum = 0; double values[10]; int i = 0; cin >> ch; while (!isalpha(ch)) { values[i] = ch; sum += values[i]; i++; cin >> ch; } What is happening is that if I enter the value 1, that gets assigned to ch as a char. Now ch is assigning it's value to a double and doing an implicit cast. So it is assigning the ASCII value of '1' to values[i]. I want it to just assign 1 to values[i]. Is there a better way to do this? Or is there something that I'm missing?

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  • base pointer to derived class

    - by Jay
    Suppose there are Base class and Derived class. Base *A = new Base; Here A is a pointer point to Base class, and new constructs one that A points to. I also saw Base *B = new Derived; How to explain this? B is a pointer to Base Class, and a Derived class constructed and pointed by B? If there is a function derived from Base class, say, Virtual void f(), and it's been overridden in Derived class, then B->f() will invoke which version of the function? version in Base class, or version that overridden in Derived Class. What if there is a new function void g()in Derived, is B->g() going to invoke this function properly? One more is, is int *a = new double; or int *a = new int; legal?

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