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  • What is an overloaded operator in c++?

    - by Jeff
    I realize this is a basic question but I have searched online, been to cplusplus.com, read through my book, and I can't seem to grasp the concept of overloaded operators. A specific example from cplusplus.com is: // vectors: overloading operators example #include <iostream> using namespace std; class CVector { public: int x,y; CVector () {}; CVector (int,int); CVector operator + (CVector); }; CVector::CVector (int a, int b) { x = a; y = b; } CVector CVector::operator+ (CVector param) { CVector temp; temp.x = x + param.x; temp.y = y + param.y; return (temp); } int main () { CVector a (3,1); CVector b (1,2); CVector c; c = a + b; cout << c.x << "," << c.y; return 0; } from http://www.cplusplus.com/doc/tutorial/classes2/ but reading through it I'm still not understanding them at all. I just need a basic example of the point of the overloaded operator (which I assume is the "CVector CVector::operator+ (CVector param)"). There's also this example from wikipedia: Time operator+(const Time& lhs, const Time& rhs) { Time temp = lhs; temp.seconds += rhs.seconds; if (temp.seconds >= 60) { temp.seconds -= 60; temp.minutes++; } temp.minutes += rhs.minutes; if (temp.minutes >= 60) { temp.minutes -= 60; temp.hours++; } temp.hours += rhs.hours; return temp; } from "http://en.wikipedia.org/wiki/Operator_overloading" The current assignment I'm working on I need to overload a ++ and a -- operator. Thanks in advance for the information and sorry about the somewhat vague question, unfortunately I'm just not sure on it at all.

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  • Simple C++ program on multidimensional arrays - Getting C2143 error among others. Not sure why?

    - by noobzilla
    Here is my simple multidimensional array program. The first error occurs where I declare the function addmatrices and then a second one where it is implemented. I am also getting an undefined variable error for bsize. What am I doing incorrectly? #include <iostream> #include <fstream> #include <string> #include <iomanip> using namespace std; //Function declarations void constmultiply (double matrixA[][4], int asize, double matrixC[][4], int bsize, double multiplier); //Pre: The address of the output file, the matrix to be multiplied by the constant, the matrix in which // the resultant values will be stored and the multiplier are passed in. //Post: The matrix is multiplied by the multiplier and the results are displayed on screen and written to the // output file. int addmatrices (double matrixA[][4], int asize, double matrixB[]4], int bsize, double matrixC[][4], int csize); //Pre: The addresses of three matrices are passed in //Post: The values in each of the two matrices are added together and put into a third matrix //Error Codes int INPUT_FILE_FAIL = 1; int UNEQUAL_MATRIX_SIZE = 2; //Constants const double multiplier = 2.5; const int rsize = 4; const int csize = 4; //Main Driver int main() { //Declare the two matrices double matrix1 [rsize][csize]; double matrix2 [rsize][csize]; double matrix3 [rsize][csize]; //Variables double temp; string filename; //Declare filestream object ifstream infile; //Ask the user for the name of the input file cout << "Please enter the name of the input file: "; cin >> filename; //Open the filestream object infile.open(filename.c_str()); //Verify that the input file opened correctly if (infile.fail()) { cout << "Input file failed to open" <<endl; exit(INPUT_FILE_FAIL); } //Begin reading in data from the first matrix for (int i = 0; i <= 3; i++)//i = row { for (int j = 0; j <= 3; j++)// j = column { infile >> temp; matrix1[i][j] = temp; } } //Begin reading in data from the second matrix for (int k = 0; k <= 3; k++)// k = row { for (int l = 0; l <= 3; l++)// l = column { infile >> temp; matrix2[k][l] = temp; } } //Notify user cout << "Input file open, reading matrices...Done!" << endl << "Read in 2 matrices..."<< endl; //Output the values read in for Matrix 1 for (int i = 0; i <= 3; i++) { for (int j = 0; j <= 3; j ++) { cout << setprecision(1) << matrix1[i][j] << setw(8); } cout << "\n"; } cout << setw(40)<< setfill('-') << "-" << endl ; //Output the values read in for Matrix 2 for (int i = 0; i <= 3; i++) { for (int j = 0; j <= 3; j ++) { cout << setfill(' ') << setprecision(2) << matrix2[i][j] << setw(8); } cout << "\n"; } cout << setw(40)<< setfill('-') << "-" << endl ; //Multiply matrix 1 by the multiplier value constmultiply (matrix1, rsize, matrix3, rsize, multiplier); //Output matrix 3 values to screen for (int i = 0; i <= 3; i++) { for (int j = 0; j <= 3; j ++) { cout << setfill(' ') << setprecision(2) << matrix3[i][j] << setw(8); } cout << "\n"; } cout << setw(40)<< setfill('-') << "-" << endl ; // //Add matrix1 and matrix2 // addmatrices (matrix1, 4, matrix2, 4, matrix3, 4); // //Finished adding. Now output matrix 3 values to screen // for (int i = 0; i <= 3; i++) // { //for (int j = 0; j <= 3; j ++) //{ // cout << setfill(' ') << setprecision(2) << matrix3[i][j] << setw(8); //} //cout << "\n"; // } // cout << setw(40)<< setfill('-') << "-" << endl ; //Close the input file infile.close(); return 0; } //Function implementation void constmultiply (double matrixA[][4], int asize, double matrixC[][4], int bsize, double multiplier) { //Loop through each row and multiply the value at that location with the multiplier for (int i = 0; i < asize; i++) { for (int j = 0; j < 4; j++) { matrixC[i][j] = matrixA[i][j] * multiplier; } } } int addmatrices (double matrixA[][4], int asize, double matrixB[]4], int bsize, double matrixC[][4], int csize) { //Remember that you can only add two matrices that have the same shape - i.e. They need to have an equal //number of rows and columns. Let's add some error checking for that: if(asize != bsize) { cout << "You are attempting to add two matrices that are not equal in shape. Program terminating!" << endl; return exit(UNEQUAL_MATRIX_SIZE); } //Confirmed that the matrices are of equal size, so begin adding elements for (int i = 0; i < asize; i++) { for (int j = 0; j < bsize; j++) { matrixC[i][j] = matrixA[i][j] + matrixB[i][j]; } } }

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  • Extend precision of MySQL's double datatype?

    - by tim82
    I am trying to save the value "6.714285714285714" into a DOUBLE datatype field. Unfortunately it does not fit at all and is cutted by one char. Storing larger numbers becomes less precise. Already searched in the mysql manual and it seems to be that double is the most precise data type available. Anyone knows a practicable workaround? Sorry for my bad english and thx a lot!

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  • What is the equivalent of REGEXP_SUBSTR in mysql?

    - by KandadaBoggu
    I want to extract a word from a string column of a table. description =========================== abc order_id: 2 xxxx yyy aa mmm order_id: 3 nn kk yw Expected result set order_id =========================== 2 3 Table will at most have 100 rows, text length is ~256 char and column always has one order_id present. So performance is not an issue. In Oracle, I can use REGEXP_SUBSTR for this problem. How would I solve this in MySQL?

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  • Cannot work for 2nd iteration because of writing delay.

    - by karikari
    My code's IF-THEN does not work for 2nd iteration. This is due to, the jar processing take some time to write it result inside the output.txt. Since the writing is a bit late, my code's 2nd iteration will always read the previous written value inside the output.txt in order to pass it to the IF-THEN. For example, in 1st iteration: output.txt -- 0.9888 twrite.txt -- msg: ok 2nd iteration: output.txt -- 0.5555 twrite.txt -- msg: ok //the IF-THEN still gives this result which is based on previous iteration. it should be msg: not ok . since it is < 0.7 I need help, how to solve this 'delay' problem? HRESULT CButtonDemoBHO::onDocumentComplete(IDispatch *pDisp, VARIANT *vUrl){ ATLTRACE("CButtonDemoBHO::onDocumentComplete %S\n", vUrl->bstrVal); WinHttpClient client(vUrl->bstrVal); client.SendHttpRequest(); wstring httpResponseHeader = client.GetHttpResponseHeader(); wstring httpResponse = client.GetHttpResponse(); writeToLog(httpResponse.c_str()); if (isMainFrame(pDisp)){ m_normalPageLoad=false; FILE *child = _popen("javaw -jar c:\\simmetrics.jar c:\\chtml.txt c:\\thtml.txt > c:\\output.txt", "r"); fclose(child); char readnumber[10]; float f = 0; FILE *file11 = fopen("c:\\output.txt","r"); char* p = fgets(readnumber,10,file11); std::istringstream iss(p); iss >> f; if (f > 0.7) { wfstream file12 ("c:\\twrite.txt", ios_base::out); file12 << "Msg: ok"; file12.close(); } else { wfstream file12 ("c:\\twrite.txt", ios_base::out); file12 << "Msg: not ok"; file12.close(); } iss.clear(); fclose(file11); return S_OK; } return S_OK; }

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  • read length of string from stdin

    - by teoz
    I want to take a string from stdin but I don't want a static array of fixed size I know that scanf need something where save the stdin input, but I can't do something like this: char string[10] scanf("%s",string); becouse I need to know before how long will be the string in order to allocate the right memory space. Can you help me to resolve this problem?

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  • what does this error mean in c?

    - by mekasperasky
    #include<stdio.h> #include<ctype.h> int main() { char a,b; FILE *fp; fp=fopen("lext.txt","w"); fprintf(fp,"PLUS"); return 0; } the error i get is this /tmp/ccQyyhxo.o:(.eh_frame+0x11): undefined reference to `__gxx_personality_v0' collect2: ld returned 1 exit status

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  • How can i declare a Binary type

    - by hamza
    i need to work with a binary number i just write : const x = 00010000 ; & it doesn't work i know that i can use an hexadecimal number that have the same value as 00010000 but for more knowledge i want to know if there is a type in C++ for binary numbers & if there isn't ,is there another solution for my Problem ? thanks

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  • html:checkbox query

    - by sarah
    Hi All, i have the following code . and in Form is have property called isActive of type char ,how would i get the checked value of it ,i am getting some symbols like 'o' if checked. I am using userform.getIsActive() ,where i am going wrong .I want 'y' or 'n' values

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  • run shell command from java

    - by Aykut
    Hi, I am working on an application an have an issue about running shell command from java application. here is the code: public String execRuntime(String cmd) { Process proc = null; int inBuffer, errBuffer; int result = 0; StringBuffer outputReport = new StringBuffer(); StringBuffer errorBuffer = new StringBuffer(); try { proc = Runtime.getRuntime().exec(cmd); } catch (IOException e) { return ""; } try { response.status = 1; result = proc.waitFor(); } catch (InterruptedException e) { return ""; } if (proc != null && null != proc.getInputStream()) { InputStream is = proc.getInputStream(); InputStream es = proc.getErrorStream(); OutputStream os = proc.getOutputStream(); try { while ((inBuffer = is.read()) != -1) { outputReport.append((char) inBuffer); } while ((errBuffer = es.read()) != -1) { errorBuffer.append((char) errBuffer); } } catch (IOException e) { return ""; } try { is.close(); is = null; es.close(); es = null; os.close(); os = null; } catch (IOException e) { return ""; } proc.destroy(); proc = null; } if (errorBuffer.length() > 0) { logger .error("could not finish execution because of error(s)."); logger.error("*** Error : " + errorBuffer.toString()); return ""; } return outputReport.toString(); } but when i try to exec command like : /export/home/test/myapp -T "some argument" myapp reads "some argument" as two seperated arguments.but I want to read "some argument" as only a argument. when i directly run this command from terminal, it executed successfully. I tried '"some argument"' ,""some argument"" , "some\ argument" but did not work for me. how can i read this argument as one argument. Thnaks.

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  • How to generate correlated binary variables

    - by jonalm
    Dear All I need to generate a series of N random binary variables with a given correlation function. Let x = {x_i} be a series of binary variables (taking the value 0 or 1, i running form 1 to N). The marginal probability is given Pr(x_i = 1) = p, and the values should be correlated in the following way E[ x_i x_j ] = const * |i-j|^-alfa where alfa is a positive number. Is it possible to generate a series like this? preferably in python.

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  • Getting following warning while compiling

    - by thetna
    warning: passing argument 1 of 'bsearch' makes pointer from integer without a cast and the corresponding code is Parent =bsearch((const size_t)ParentNum, ClauseVector, Size, sizeof(CLAUSE),pcheck_CompareNumberAndClause); the compilar is gcc. here CLAUSE is defined as *CLAUSE.

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  • Internet Explorer 8 + Deflate

    - by Andreas Bonini
    I have a very weird problem.. I really do hope someone has an answer because I wouldn't know where else to ask. I am writing a cgi application in C++ which is executed by Apache and outputs HTML code. I am compressing the HTML output myself - from within my C++ application - since my web host doesn't support mod_deflate for some reason. I tested this with Firefox 2, Firefox 3, Opera 9, Opera 10, Google Chrome, Safari, IE6, IE7, IE8, even wget.. It works with ANYTHING except IE8. IE8 just says "Internet Explorer cannot display the webpage", with no information whatsoever. I know it's because of the compression only because it works if I disable it. Do you know what I'm doing wrong? I use zlib to compress it, and the exact code is: /* Compress it */ int compressed_output_size = content.length() + (content.length() * 0.2) + 16; char *compressed_output = (char *)Alloc(compressed_output_size); int compressed_output_length; Compress(compressed_output, compressed_output_size, (void *)content.c_str(), content.length(), &compressed_output_length); /* Send the compressed header */ cout << "Content-Encoding: deflate\r\n"; cout << boost::format("Content-Length: %d\r\n") % compressed_output_length; cgiHeaderContentType("text/html"); cout.write(compressed_output, compressed_output_length); static void Compress(void *to, size_t to_size, void *from, size_t from_size, int *final_size) { int ret; z_stream stream; stream.zalloc = Z_NULL; stream.zfree = Z_NULL; stream.opaque = Z_NULL; if ((ret = deflateInit(&stream, CompressionSpeed)) != Z_OK) COMPRESSION_ERROR("deflateInit() failed: %d", ret); stream.next_out = (Bytef *)to; stream.avail_out = (uInt)to_size; stream.next_in = (Bytef *)from; stream.avail_in = (uInt)from_size; if ((ret = deflate(&stream, Z_NO_FLUSH)) != Z_OK) COMPRESSION_ERROR("deflate() failed: %d", ret); if (stream.avail_in != 0) COMPRESSION_ERROR("stream.avail_in is not 0 (it's %d)", stream.avail_in); if ((ret = deflate(&stream, Z_FINISH)) != Z_STREAM_END) COMPRESSION_ERROR("deflate() failed: %d", ret); if ((ret = deflateEnd(&stream)) != Z_OK) COMPRESSION_ERROR("deflateEnd() failed: %d", ret); if (final_size) *final_size = stream.total_out; return; }

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  • OpenGL Coordinate system confusion

    - by user146780
    Maybe I set up GLUT wrong. Basically I want verticies to be reletive to their size in pixels. Ex:right now if I create a hexagon, it hakes up the whole screen even though the units are 6. #include <iostream> #include <stdlib.h> //Needed for "exit" function #include <cmath> //Include OpenGL header files, so that we can use OpenGL #ifdef __APPLE__ #include <OpenGL/OpenGL.h> #include <GLUT/glut.h> #else #include <GL/glut.h> #endif using namespace std; //Called when a key is pressed void handleKeypress(unsigned char key, //The key that was pressed int x, int y) { //The current mouse coordinates switch (key) { case 27: //Escape key exit(0); //Exit the program } } //Initializes 3D rendering void initRendering() { //Makes 3D drawing work when something is in front of something else glEnable(GL_DEPTH_TEST); } //Called when the window is resized void handleResize(int w, int h) { //Tell OpenGL how to convert from coordinates to pixel values glViewport(0, 0, w, h); glMatrixMode(GL_PROJECTION); //Switch to setting the camera perspective //Set the camera perspective glLoadIdentity(); //Reset the camera gluPerspective(45.0, //The camera angle (double)w / (double)h, //The width-to-height ratio 1.0, //The near z clipping coordinate 200.0); //The far z clipping coordinate } //Draws the 3D scene void drawScene() { //Clear information from last draw glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); //Reset the drawing perspective glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); glBegin(GL_POLYGON); //Begin quadrilateral coordinates //Trapezoid glColor3f(255,0,0); for(int i = 0; i < 6; ++i) { glVertex2d(sin(i/6.0*2* 3.1415), cos(i/6.0*2* 3.1415)); } glEnd(); //End quadrilateral coordinates glutSwapBuffers(); //Send the 3D scene to the screen } int main(int argc, char** argv) { //Initialize GLUT glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH); glutInitWindowSize(400, 400); //Set the window size //Create the window glutCreateWindow("Basic Shapes - videotutorialsrock.com"); initRendering(); //Initialize rendering //Set handler functions for drawing, keypresses, and window resizes glutDisplayFunc(drawScene); glutKeyboardFunc(handleKeypress); glutReshapeFunc(handleResize); glutMainLoop(); //Start the main loop. glutMainLoop doesn't return. return 0; //This line is never reached } How can I make it so that a polygon of 0,0 10,0 10,10 0,10 defines a polygon starting at the top left of the screen and is a width and height of 10 pixels? Thanks

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  • Win32 C/C++ Load Image from memory buffer

    - by Bruno
    I want to load a image (.bmp) file on a Win32 application, but I do not want to use the standard LoadBitmap/LoadImage from Windows API: I want it to load from a buffer that is already in memory. I can easily load a bitmap directly from file and print it on the screen, but this issue is making me stuck :( What I'm looking for is a function that works like this: HBITMAP LoadBitmapFromBuffer(char* buffer, int width, int height); Thanks.

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  • Parameter has no walue

    - by Simon
    string queryString = "SELECT SUM(skupaj_kalorij)as Skupaj_Kalorij " + "FROM (obroki_save LEFT JOIN users ON obroki_save.ID_uporabnika=users.ID)" + "WHERE users.ID= " + a.ToString() + " AND obroki_save.datum =?"; using (OleDbCommand cmd = new OleDbCommand(queryString,database)) { cmd.Parameters.Add("@datum", OleDbType.Char).Value = DateTime.Now.ToShortDateString(); } Why doesn't the parametr datum get the date value? (the value of at least one complex parameter has not been determined )

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  • Implementing default constructors

    - by James
    Implement the default constructor, the constructors with one and two int parameters. The one-parameter constructor should initialize the first member of the pair, the second member of the pair is to be 0. Overload binary operator + to add the pairs as follows: (a, b) + (c, d) = (a + c, b + d); Overload the - analogously. Overload the * on pairs ant int as follows: (a, b) * c = (a * c, b * c). Write a program to test all the member functions and overloaded operators in your class definition. You will also need to write accessor (get) functions for each member. The definition of the class Pairs: class Pairs { public: Pairs(); Pairs(int first, int second); Pairs(int first); // other members and friends friend istream& operator>> (istream&, Pair&); friend ostream& operator<< (ostream&, const Pair&); private: int f; int s; }; Self-Test Exercise #17: istream& operator (istream& ins, Pair& second) { char ch; ins ch; // discard init '(' ins second.f; ins ch; // discard comma ',' ins second.s; ins ch; // discard final '(' return ins; } ostream& operator<< (ostream& outs, const Pair& second) { outs << '('; outs << second.f; outs << ", " ;// I followed the Author's suggestion here. outs << second.s; outs << ")"; return outs; }

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  • Fundamental types

    - by smerlin
    I always thought the following types are "fundamental types", so i thought my anwser to this question would be correct, but surprisingly it got downvoted... Searching the web, i found this. So, IBM says aswell those types are fundamental types.. Well how do you interpret the Standard, are following types (and similar types), "fundamental types" according to the c++ standard ? unsigned int signed char long double long long long long int unsigned long long int

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  • Parsing numbers at PreviewTextInput

    - by Nitin Chaudhari
    I have a WPF application in which I have a hook at PreviewTextInput, through that I get the currently entered character and I have the string already entered. Given this I need to write the following function : bool ShouldAccept(char newChar,string existingText) existingText can be comma seperated valid numbers(including exponential) and it should just return false when invalid characters are pressed. My code(if else based) currently has a lot of flaws, I wanted to know if there is any smart way to do it.

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  • How to provide default argument as this object?

    - by atch
    I would like to have declaration like this: void Date::get_days_name(const Date& = this) which I would understand that if no argument is provided use this object as an argument. For some reason in VS I'm getting err msg: 'Error 1 error C2355: 'this' : can only be referenced inside non-static member ' Any idea what I'm doing wrong?

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