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  • include and using namespace in C++

    - by cambr
    for using cout, I need to specify both: #include<iostream> and using namespace std; Where is cout defined? in iostream, correct? So, it is that iostream itself is there in namespace std? What is the meaning of both the statements with respect to using cout? I am confused why we need to include them both.

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  • C++ destructor problem with boost::scoped_ptr

    - by bb-generation
    I have a question about the following code: #include <iostream> #include <boost/scoped_ptr.hpp> class Interface { }; class A : public Interface { public: A() { std::cout << "A()" << std::endl; } virtual ~A() { std::cout << "~A()" << std::endl; } }; Interface* get_a() { A* a = new A; return a; } int main() { { std::cout << "1" << std::endl; boost::scoped_ptr<Interface> x(get_a()); std::cout << "2" << std::endl; } std::cout << "3" << std::endl; } It creates the following output: 1 A() 2 3 As you can see, it doesn't call the destructor of A. The only way I see to get the destructor of A being called, is to add a destructor for the Interface class like this: virtual ~Interface() { } But I really want to avoid any Implementation in my Interface class and virtual ~Interface() = 0; doesn't work (produces some linker errors complaining about a non existing implementation of ~Interface(). So my question is: What do I have to change in order to make the destructor being called, but (if possible) leave the Interface as an Interface (only abstract methods).

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  • expected `;' before "pennies"? C++ Debugging (Code Completed)

    - by Josh Lake
    Can anyone tell me why I get an error on my last cout? #include <iostream> #include <cmath> #include <stdio.h> #include <cstring> #include <conio.h> using namespace std; inline void keep_window_open() { char ch; cin>>ch; } int main() { cout << "How many pennies do you have?\n"; int pennies; cin >> pennies; double total_pen; total_pen = (0.01 * pennies); if (pennies >= 1) { string penn = " pennies."; }else { string penn = " penny."; } cout << "How many nickles do you have?\n"; int nickles; cin >> nickles; double total_nic; total_nic = (0.05 * nickles); if (nickles >= 1) { string five = " nickels."; }else { string five = " nickel."; } cout << "How many dimes do you have?\n"; int dimes; cin >> dimes; double total_dim; total_dim = (0.10 * dimes); if (dimes >= 1) { string ten = " dimes."; }else { string ten = " dime."; } cout << "How many quarters do you have?\n"; int quarters; cin >> quarters; double total_qua; total_qua = (0.25 * quarters); if (quarters >= 1) { string twentyfive = " quarters."; }else { string twentyfive = " quarter."; } cout << "How many half-dollars do you have?\n"; int half_dollars; cin >> half_dollars; double total_dol; total_dol = (0.50 * half_dollars); if (half_dollars >= 1) { string fifty = " half dollars."; }else { string fifty = " half dollar."; } string saying = "You have "; cout << saying pennies penn << "\n" << saying nickles five << "\n" << saying dimes ten << "\n" << saying quarters twentyfive << "\n" << saying half_dollars fifty << "\n"; keep_window_open() return 0; }

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  • Dynamic loaded libraries and shared global symbols

    - by phlipsy
    Since I observed some strange behavior of global variables in my dynamically loaded libraries, I wrote the following test. At first we need a statically linked library: The header test.hpp #ifndef __BASE_HPP #define __BASE_HPP #include <iostream> class test { private: int value; public: test(int value) : value(value) { std::cout << "test::test(int) : value = " << value << std::endl; } ~test() { std::cout << "test::~test() : value = " << value << std::endl; } int get_value() const { return value; } void set_value(int new_value) { value = new_value; } }; extern test global_test; #endif // __BASE_HPP and the source test.cpp #include "base.hpp" test global_test = test(1); Then I wrote a dynamically loaded library: library.cpp #include "base.hpp" extern "C" { test* get_global_test() { return &global_test; } } and a client program loading this library: client.cpp #include <iostream> #include <dlfcn.h> #include "base.hpp" typedef test* get_global_test_t(); int main() { global_test.set_value(2); // global_test from libbase.a std::cout << "client: " << global_test.get_value() << std::endl; void* handle = dlopen("./liblibrary.so", RTLD_LAZY); if (handle == NULL) { std::cout << dlerror() << std::endl; return 1; } get_global_test_t* get_global_test = NULL; void* func = dlsym(handle, "get_global_test"); if (func == NULL) { std::cout << dlerror() << std::endl; return 1; } else get_global_test = reinterpret_cast<get_global_test_t*>(func); test* t = get_global_test(); // global_test from liblibrary.so std::cout << "liblibrary.so: " << t->get_value() << std::endl; std::cout << "client: " << global_test.get_value() << std::endl; dlclose(handle); return 0; } Now I compile the statically loaded library with g++ -Wall -g -c base.cpp ar rcs libbase.a base.o the dynamically loaded library g++ -Wall -g -fPIC -shared library.cpp libbase.a -o liblibrary.so and the client g++ -Wall -g -ldl client.cpp libbase.a -o client Now I observe: The client and the dynamically loaded library possess a different version of the variable global_test. But in my project I'm using cmake. The build script looks like this: CMAKE_MINIMUM_REQUIRED(VERSION 2.6) PROJECT(globaltest) ADD_LIBRARY(base STATIC base.cpp) ADD_LIBRARY(library MODULE library.cpp) TARGET_LINK_LIBRARIES(library base) ADD_EXECUTABLE(client client.cpp) TARGET_LINK_LIBRARIES(client base dl) analyzing the created makefiles I found that cmake builds the client with g++ -Wall -g -ldl -rdynamic client.cpp libbase.a -o client This ends up in a slightly different but fatal behavior: The global_test of the client and the dynamically loaded library are the same but will be destroyed two times at the end of the program. Am I using cmake in a wrong way? Is it possible that the client and the dynamically loaded library use the same global_test but without this double destruction problem?

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  • c++ programming- Tryin to get a number within an array that is twice the average

    - by max
    i have been assigned to set up an array with points. I am told to get the maximum value, average, nd within this same array, if any point in the array is twice the average, i should cout an "outlier." So far i have gotten the average and maximum numbers in the array. but i am unable to set the programme to cout the outlier. Instead it gives me a multiple of the average. pls help! here is the programme; int main() { const int max = 10; int ary[max]={4, 32, 9, 7, 14, 12, 13, 17, 19, 18}; int i,maxv; double out,sum=0; double av; maxv= ary[0]; for(i=0; i } cout<<"maximum value: "< for(i=0; i sum = sum + ary[i]; av = sum / max; } cout<<"average: "< out = av * 2; if(ary[i]out) { cout<<"outlier: "< return 0; }

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  • How would I implement code in a .h file into the main.cpp file?

    - by Lea
    I have a c++ project I am working on. I am a little stumped at the moment. I need a little help. I need to implement code from the .h file into the main.cpp file and I am not sure how to do that. For example code code from main.cpp: switch (choice){ case 1: // open an account { cout << "Please enter the opening balence: $ "; cin >> openBal; cout << endl; cout << "Please enter the account number: "; cin >> accountNum; cout << endl; break; } case 2:// check an account { cout << "Please enter the account number: "; cin >> accountNum; cout << endl; break; } and code from the .h file: void display(ostream& out) const; // displays every item in this list through out bool retrieve(elemType& item) const; // retrieves item from this list // returns true if item is present in this list and // element in this list is copied to item // false otherwise // transformers void insert(const elemType& item); // inserts item into this list // preconditions: list is not full and // item not present in this list // postcondition: item is in this list In the .h file you would need to use the void insert under transformer in the main.cpp under case 1. How would you do that? Any help is apprecaited. I hope I didn't confuse anyone on what I am needing to know how to do. Thanks

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  • Reverse String Error?

    - by R41nB0w M47r1z
    I am creating this revese string App but i get a error if i include a space in the string ! #include <iostream> #include <string> using namespace std; int main() { int inputa; cout<<"%%%%%%%%%%%%%%%%%%String Reversing App%%%%%%%%%%%%%%%%%%%%%%%%"<<endl<<endl; cout<<"\nEnter 1 to continue and 0 to exit"<<endl<<endl; cin>>inputa; if(inputa!=0) { do { string a,c=""; cout<<"\nEnter the string you want to Reverse : "; cin>>a; for(int x=a.length()-1; x>=0; x--) { c=c+a.substr(x,1); } cout<<"\nThe Reverse String is : "<<c<<endl; cout<<"\nEnter 1 to continue and 0 to exit"<<endl<<endl; cin>>inputa; } while(inputa!=0); } //not my home work } If I type the following string like "abc def" there i get an error . But otherwise it works perfectly ! Is there some mistake with the codes ! I am new to CPP so it would be helpful if you could help me !

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  • Errors not printing correctly..Is this logic flow correct? c++

    - by igor
    Example user input: PA1 9 //correct PJ1 9 //wrong, error printed "Invalid row" because it is not between A and I PA11 9 //wrong, error printer "Invalid column" because it is not between 1 and 9. The problem I am having is that it should clear the remaining input and then ask for the user to enter the "move" again, and it is not. Where did I go wrong? I've been at it for a while and still got no progress.. void clearInput() { cin.clear(); } bool getCoords(int & x, int & y) { char row; while(true){ cin>>row>>y; row=toupper(row); if(/*(id=='P' || id=='p' || id=='D' || id=='d') && */row>='A' && row<='I' && isalpha(row) && y>=1 && y<=9){ x=row-'A'; y=y-1; return true; } else if(!(y>=1 && y<=9)){ cout<<"Invalid column\n"<< endl << endl; cout<<y; clearInput(); cout<<y; //return false; } else{ cout<<"Invalid row\n"<< endl << endl; clearInput(); //cout<<x<<y; //return false; } } }

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  • Long numbers. Division.

    - by user577395
    Hello, world! I have a problem. Today I tried to create a code, which finds Catalan number. But in my program can be long numbers. I found numerator and denominator. But i can't div long numbers! Also, only standard libraries was must use in this program. Help me please. This is my code #include <vector> #include <iostream> using namespace std; int main(int argc, char *argv[]) { const int base = 1000*1000*1000; vector <int> a, b; int n, carry = 0; cin>>n; a.push_back(n); for (int ii=n+2; ii!=(2*n)+1;++ii) { carry = 0; for (size_t i=0; i<a.size() || carry; ++i) { if (i == a.size()) a.push_back (0); long long cur = carry + a[i] * 1ll * ii; a[i] = int (cur % base); carry = int (cur / base); } } while (a.size() > 1 && a.back() == 0) a.pop_back(); b.push_back(n); for (int ii=1; ii!=n+1;++ii) { carry = 0; for (size_t i=0; i<b.size() || carry; ++i) { if (i == b.size()) b.push_back (0); long long cur = carry + b[i] * 1ll * ii; b[i] = int (cur % base); carry = int (cur / base); } } while (b.size() > 1 && b.back() == 0) b.pop_back(); cout<<(a.empty() ? 0 : a.back()); for (int i=(int)a.size()-2; i>=0; --i) cout<<(a[i]); cout<<" "; cout<<(b.empty() ? 0 : b.back()); for (int i=(int)b.size()-2; i>=0; --i) cout<<(b[i]); //system("PAUSE"); cout<<endl; return 0; } P.S. Sorry for my bad english =)

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  • c++ file bad bit

    - by user230911
    Hi, when I run this code, the open and seekg and tellg operation all success. but when I read it, it fails, the eof,bad,fail bit are 0 1 1. What can cause a file bad? thanks int readriblock(int blockid, char* buffer) { ifstream rifile("./ri/reverseindex.bin", ios::in|ios::binary); rifile.seekg(blockid * RI_BLOCK_SIZE, ios::beg); if(!rifile.good()){ cout<<"block not exsit"<<endl; return -1;} cout<<rifile.tellg()<<endl; rifile.read(buffer, RI_BLOCK_SIZE); **cout<<rifile.eof()<<rifile.bad()<<rifile.fail()<<endl;** if(!rifile.good()){ cout<<"error reading block "<<blockid<<endl; return -1;} rifile.close(); return 0; }

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  • how do I use an enum value on a switch statement in C++

    - by BotBotPgm
    I would like to use an enum value for my switch statment in C++. Is it possible to use the enum values enclosed in the "{}" as choices for the "switch()"? I know that switch() needs an integer value in order to direct the flow of programming to the appropriate case number. If this is the case, do I just make a variable for each constant in the 'enum' statment? I also want the user to be able to pick the choice and pass that choice to the switch() statement. for example: cout<< "1 - Easy"; cout<<"2 - Medium"; cout<< "3 -Hard"; enum myChoice {EASY =1 ,MEDIUM = 2, HARD = 3} cin ???? switch(????) case 1/EASY: (can I just type case EAST?) cout << "You picked easy!"; break; case 2/MEDIUM: cout << "You picked medium!"; case 3..... (same thing as case 2 except on hard.) default: return 0; Thanks

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  • Why does my program not react to any arguments?

    - by Electric Coffee
    I have a simple test program in C++ that prints out attributes of a circle #include <iostream> #include <stdlib.h> #include "hidden_functions.h" // contains the Circle class using namespace std; void print_circle_attributes(float r) { Circle* c = new Circle(r); cout << "radius: " << c->get_radius() << endl; cout << "diameter: " << c->get_diameter() << endl; cout << "area: " << c->get_area() << endl; cout << "circumference: " << c->get_circumference() << endl; cout << endl; delete c; } int main(int argc, const char* argv[]) { float input = atof(argv[0]); print_circle_attributes(input); return 0; } when I run my program with the parameter 2.4 it outputs: radius: 0.0 diameter: 0.0 area: 0.0 circumference: 0.0 I've previously tested the program without the parameter, but simply using static values, and it ran just fine; so I know there's nothing wrong with the class I made... So what did I do wrong here? Note: the header is called hidden_functions.h because it served to test out how it would work if I had functions not declared in the header

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  • How can I draw a line with a variable of width?

    - by user1729944
    #include <iostream> #include <cmath> #include "graph1.h" using namespace std; int main() { int diameter = 0; int height = 0; double rate = 0; char repeat = 'y'; int obj_num = 0; displayGraphics(); obj_num = drawRect(0,0,50,400); setColor(obj_num,200,200,200); obj_num = drawRect(0,400,640,79); setColor(obj_num,71,35,35); obj_num = drawLine(50,50,150,50,5); setColor(obj_num,80,80,80); displayBMP("faucet.bmp",150,12); do { do { cout << "Enter the diamater of the cylinder <in inches > 0 but <= 300: "; cin >> diameter; if((diameter<0) || (diameter>300)) { cout << "Incorrect diamater entered; value must be between 1 and 300" << endl; } }while((diameter<0) || (diameter>300)); do { cout << "Enter the height of the cylinder <in inches > 0 but <= 325: "; cin >> height; if((height<0) || (height>325)) { cout << "Incorrect height entered; value must be between 1 and 325" << endl; } }while((height<0) || (height>325)); do { cout << "Enter the facet water's rate: <gallons/minute> "; cin >> rate; if((rate<0) || (rate>100)) { cout << "Incorrect rate entered; value must be between 1 and 100" << endl; } }while((rate<0) || (rate>100)); //I need to draw the lines here. The graphics window has a faucet that is supposed to fill //up a cylinder made out of 3 lines. I don't know how to make the lines vary from the users //input since lines are hard coded with points and all i am receiving is the width for the //bottom line and the height for the left and right lines. cout << "Repeat program? (y/n): "; cin >> repeat; clearGraphics(); }while ( (repeat == 'y') || (repeat == 'Y') ); return 0; } Here is a screenshot for reference:

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  • c++ problem, maybe with types...

    - by Infinity
    Hi guys! I have a little problem in my code. The variables don't want to change their values. Can you say why? Here is my code: vector<coordinate> rocks(N); double angle; double x, y; // other code while (x > 1.0 || x < -1.0 || y > 1.0 || y < -1.0) { angle = rand() * 2.0 * M_PI; cout << angle << endl; cout << rocks[i - 1].x << endl; cout << rocks[i - 1].y << endl; x = rocks[i-1].x + r0 * cos(angle); y = rocks[i-1].y + r0 * sin(angle); cout << x << endl; cout << y << endl << endl; } // other code And the result on the console is: 6.65627e+09 0.99347 0.984713 1.09347 0.984713 1.16964e+09 0.99347 0.984713 1.09347 0.984713 As you see the values of x, y variables doesn't change and this while be an infinity loop. What's the problem? What do you think?

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  • C++ dynamic array sizing problem

    - by Peter
    The basic pseudo code looks like this: void myFunction() { int size = 10; int * MyArray; MyArray = new int[size]; cout << size << endl; cout << sizeof(MyArray) << endl; } The first cout returns 10, as expected, while the second cout returns 4. Anyone have an explanation?

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  • Finding the Largest and Smallest Integers In A Set- Basic

    - by Ka112324
    I'm kind of on the right track, however my output is not quite right. The program asks for the number of integers you have and then it asks for those numbers. For an example is says please enter the number of integers, you can put 3. And then you enter 3 numbers. I can't use arrays because I am a beginner student and we have not learned those yet. Using count is the only way that allows me to input integers. What do I need to add to my program? Again I am a general computer science student so I can't use anything advanced. I used include iostream, namespace int main and all that you just cant see it int data; int num; int count=0; int max=0; do { cout<<"Enter the number of intergers"<<endl; cin>>num; while (count<num) { cout<<"Please enter a number"<<endl; cin>>data; count++; if (data<min) { min=data; } if (data>max) { max=data; } } cout<<"Smallest integer:"<<min<<endl; cout<<"Largest integer:"<<max<<endl; cout<<"Would you like to continue?"<<endl; cin>>ans; } while ((ans=='y')||(ans=='Y')); return 0; }

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  • Feedback + Bad output

    - by user1770094
    So I've got an assignment I think I'm more or less done with, but there is something which is messing up the output badly somewhere down the line, or even the calculation, and I don't see where the problem is. The assignment is to make a game in which a certain ammount of players run up through a tunnel towards a spot,where they will stop and spin around it,and then their dizziness is supposed to make them randomly either progress towards goal or regress back towards start.And each time they get another spot closer to goal,they get another "marking",and it goes on like this until one of them reaches goal. The program includes three files: one main.cpp,one header file and another cpp file. The header file: #ifndef COMPETITOR_H #define COMPETITOR_H #include <string> using namespace std; class Competitor { public: void setName(); string getName(); void spin(); void move(); int checkScore(); void printResult(); private: string name; int direction; int markedSpots; }; #endif // COMPETITOR_H The second cpp file: #include <iostream> #include <string> #include <cstdlib> #include <ctime> #include "Competitor.h" using namespace std; void Competitor::setName() { cin>>name; } string Competitor::getName() { return name; } void Competitor::spin() { srand(time(NULL)); direction = rand()%1+0; } void Competitor::move() { if(direction == 1) { markedSpots++; } else if(direction == 0 && markedSpots != 0) { markedSpots--; } } int Competitor::checkScore() { return markedSpots; } void Competitor::printResult() { if(direction == 1) { cout<<" is heading towards goal and has currently "<<markedSpots<<" markings."; } else if(direction == 0) { cout<<"\n"<<getName()<<" is heading towards start and has currently "<<markedSpots<<" markings."; } } The main cpp file: #include <iostream> #include <string> #include <cstdlib> #include <ctime> #include "Competitor.h" using namespace std; void inputAndSetNames(Competitor comps[],int nrOfComps); void makeTwist(Competitor comps[],int nrOfComps); void makeMove(Competitor comps[],int nrOfComps); void showAll(Competitor comps[],int nrOfComps); int winner(Competitor comps[],int nrOfComps, int nrOfTwistPlaces); int main() { int nrOfTwistPlaces; int nrOfComps; int noWinner = -1; int laps = 0; cout<<"How many spinning places should there be? "; cin>>nrOfTwistPlaces; cout<<"How many competitors should there be? "; cin>>nrOfComps; Competitor * comps = new Competitor[nrOfComps]; inputAndSetNames(comps, nrOfComps); do { laps++; cout<<"\nSpin "<<laps<<":"; makeTwist(comps, nrOfComps); makeMove(comps, nrOfComps); showAll(comps, nrOfComps); }while(noWinner == -1); delete [] comps; return 0; } void inputAndSetNames(Competitor comps[],int nrOfComps) { cout<<"Type in the names of the "<<nrOfComps<<" competitors:\n"; for(int i=0;i<nrOfComps;i++) { comps[i].setName(); } cout<<"\n"; } void makeTwist(Competitor comps[],int nrOfComps) { for(int i=0;i<nrOfComps;i++) { comps[i].spin(); } } void makeMove(Competitor comps[],int nrOfComps) { for(int i=0;i<nrOfComps;i++) { comps[i].move(); } } void showAll(Competitor comps[],int nrOfComps) { for(int i=0;i<nrOfComps;i++) { comps[i].printResult(); } cout<<"\n\n"; system("pause"); } int winner(Competitor comps[],int nrOfComps, int nrOfTwistPlaces) { int end = 0; int score = 0; for(int i=0;i<nrOfComps;i++) { score = comps[i].checkScore(); if(score == nrOfTwistPlaces) { end = 1; } else end = -1; } return end; } I'd be grateful if you would point out other mistakes if you see any.Thanks in advance.

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  • std::thread and class constructor and destructor

    - by toeplitz
    When testing threads in C++11 I have created the following example: #include <iostream> #include <thread> class Foo { public: Foo(void) { std::cout << "Constructor called: " << this << std::endl; } ~Foo(void) { std::cout << "Destructor called: " << this << std::endl; } void operator()() const { std::cout << "Operatior called: " << this << std::endl; } }; void test_normal(void) { std::cout << "====> Standard example:" << std::endl; Foo f; } void test_thread(void) { std::cout << "====> Thread example:" << std::endl; Foo f; std::thread t(f); t.detach(); } int main(int argc, char **argv) { test_normal(); test_thread(); for(;;); } Which prints the following: Why is the destructor called 6 times for the thread? And why does the thread report different memory locations?

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  • Win conditions for a connect-4 like game

    - by FrozenWasteland
    I have an 5x10 array that is populated with random values 1-5. I want to be able to check when 3 numbers, either horizontally, or vertically, match. I can't figure out a way to do this without writing a ton of if statements. Here is the code for the randomly populated array int i; int rowincrement = 10; int row = 0; int col = 5; int board[10][5]; int randomnum = 5; int main(int argc, char * argv[]) { srand(time(NULL)); cout << "============\n"; while(row < rowincrement) { for(i = 0; i < 5; i++) { board[row][col] = rand()%5 + 1; cout << board[row][col] << " "; } cout << endl; cout << "============\n"; row++; } cout << endl; return 0; }

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  • c++ Multiple Inheritance - Compiler modifying my pointers

    - by Bob
    If I run the following code, I get different addresses printed. Why? class Base1 { int x; }; class Base2 { int y; }; class Derived : public Base1, public Base2 { }; union U { Base2* b; Derived* d; U(Base2* b2) : b(b) {} }; int main() { Derived* d = new Derived; cout << d << "\n"; cout << U(d).d << "\n"; return 0; } Even more fun is if you repeatedly go in and out of the union the address keeps incrementing by 4, like this int main() { Derived* d = new Derived; cout << d << "\n"; d = U(d).d; cout << d << "\n"; d = U(d).d; cout << d << "\n"; return 0; } If the union is modified like this, then the problem goes away union U { void* v; Base2* b; Derived* d; U(void* v) : v(v) {} }; Also, if either base class is made empty, the problem goes away. Is this a compiler bug? I want it to leave my pointers the hell alone.

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  • Why won't this piece of my code write to file

    - by user2934783
    I am developing a c++ banking system. I am able to get the float, newbal, values correctly and when I try to write to file, there is no data in the file. else { file>>firstname>>lastname; cout<<endl<<firstname<<" "<<lastname<<endl; cout<<"-----------------------------------\n"; string line; while (getline(file, line)) { //stringstream the getline for line string in file istringstream iss(line); if (iss >> date >> amount) { cout<<date<<"\t\t$"<<showpoint<<fixed<<setprecision(2)<<amount<<endl; famount+=amount; } } cout<<"Your balance is $"<<famount<<endl; cout<<"How much would you like to deposit today: $"; cin>>amountinput; float newbal=0; newbal=(famount+=amountinput); cout<<"\nYour new balance is: $"<<newbal<<".\n"; file<<date<<"\t\t"<<newbal; //***This should be writing to file but it doesn't. file.close(); The text file looks like this: Tony Gaddis 05/24/12 100 05/30/12 300 07/01/12 -300 //Console Output looks like this Tony Gaddis 05/24/12 100 05/30/12 300 07/01/12 -300 Your balance is: #1 How much wuld you like to deposit: #2 Your new balance is: #1 + #2 write to file close file. //exits to main loop:::: How can I make it write to file and save it, and why is this happening. I tried doing it with ostringstream as well considering how I used istringstream for the input. But it didn't work either :\ float newbal=0; newbal=(famount+=amountinput); ostringstream oss(newbal); oss<<date<<"\t\t"<<newbal; I am trying to self teach c++ so any relevant information would be kindly appreciated.

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  • C++ Perfect Number. Need some help revising.

    - by user278330
    I need some help revising this. It keeps only displaying 0s as the temp. Thank you. // A program to determine whether the input number is a perfect number // A perfect number is defined by the sum of all its positive divisors excluding itself // 28: 1+2+3+7+14 = 28. int perfect, limit, divisor; cout << "Please enter a positive integer in order to define whether it is a perfect integer or not: " ; cin >> perfect; cout << endl; int temp = 0; int prevtemp = 0; limit = 1; divisor = 1; while (limit < perfect) { if ((perfect % divisor) == 0) divisor = prevtemp; limit++; divisor++; temp = prevtemp + temp; cout << temp << endl; } if (perfect == temp) cout << "Your number is a perfect number!" << endl; else cout << "Your number is not a perfect number" << endl; return 0;

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  • Negamax implementation doesn't appear to work with tic-tac-toe

    - by George Jiglau
    I've implemented Negamax as it can be found on wikipedia, which includes alpha/beta pruning. However, it seems to favor a losing move, which should be an invalid result. The game is Tic-Tac-Toe, I've abstracted most of the game play so it should be rather easy to spot an error within the algorithm. Here is the code, nextMove, negamax or evaluate are probably the functions that contain the fault: #include <list> #include <climits> #include <iostream> //#define DEBUG 1 using namespace std; struct Move { int row, col; Move(int row, int col) : row(row), col(col) { } Move(const Move& m) { row = m.row; col = m.col; } }; struct Board { char player; char opponent; char board[3][3]; Board() { } void read(istream& stream) { stream >> player; opponent = player == 'X' ? 'O' : 'X'; for(int row = 0; row < 3; row++) { for(int col = 0; col < 3; col++) { char playa; stream >> playa; board[row][col] = playa == '_' ? 0 : playa == player ? 1 : -1; } } } void print(ostream& stream) { for(int row = 0; row < 3; row++) { for(int col = 0; col < 3; col++) { switch(board[row][col]) { case -1: stream << opponent; break; case 0: stream << '_'; break; case 1: stream << player; break; } } stream << endl; } } void do_move(const Move& move, int player) { board[move.row][move.col] = player; } void undo_move(const Move& move) { board[move.row][move.col] = 0; } bool isWon() { if (board[0][0] != 0) { if (board[0][0] == board[0][1] && board[0][1] == board[0][2]) return true; if (board[0][0] == board[1][0] && board[1][0] == board[2][0]) return true; } if (board[2][2] != 0) { if (board[2][0] == board[2][1] && board[2][1] == board[2][2]) return true; if (board[0][2] == board[1][2] && board[1][2] == board[2][2]) return true; } if (board[1][1] != 0) { if (board[0][1] == board[1][1] && board[1][1] == board[2][1]) return true; if (board[1][0] == board[1][1] && board[1][1] == board[1][2]) return true; if (board[0][0] == board[1][1] && board[1][1] == board[2][2]) return true; if (board[0][2] == board [1][1] && board[1][1] == board[2][0]) return true; } return false; } list<Move> getMoves() { list<Move> moveList; for(int row = 0; row < 3; row++) for(int col = 0; col < 3; col++) if (board[row][col] == 0) moveList.push_back(Move(row, col)); return moveList; } }; ostream& operator<< (ostream& stream, Board& board) { board.print(stream); return stream; } istream& operator>> (istream& stream, Board& board) { board.read(stream); return stream; } int evaluate(Board& board) { int score = board.isWon() ? 100 : 0; for(int row = 0; row < 3; row++) for(int col = 0; col < 3; col++) if (board.board[row][col] == 0) score += 1; return score; } int negamax(Board& board, int depth, int player, int alpha, int beta) { if (board.isWon() || depth <= 0) { #if DEBUG > 1 cout << "Found winner board at depth " << depth << endl; cout << board << endl; #endif return player * evaluate(board); } list<Move> allMoves = board.getMoves(); if (allMoves.size() == 0) return player * evaluate(board); for(list<Move>::iterator it = allMoves.begin(); it != allMoves.end(); it++) { board.do_move(*it, -player); int val = -negamax(board, depth - 1, -player, -beta, -alpha); board.undo_move(*it); if (val >= beta) return val; if (val > alpha) alpha = val; } return alpha; } void nextMove(Board& board) { list<Move> allMoves = board.getMoves(); Move* bestMove = NULL; int bestScore = INT_MIN; for(list<Move>::iterator it = allMoves.begin(); it != allMoves.end(); it++) { board.do_move(*it, 1); int score = -negamax(board, 100, 1, INT_MIN + 1, INT_MAX); board.undo_move(*it); #if DEBUG cout << it->row << ' ' << it->col << " = " << score << endl; #endif if (score > bestScore) { bestMove = &*it; bestScore = score; } } if (!bestMove) return; cout << bestMove->row << ' ' << bestMove->col << endl; #if DEBUG board.do_move(*bestMove, 1); cout << board; #endif } int main() { Board board; cin >> board; #if DEBUG cout << "Starting board:" << endl; cout << board; #endif nextMove(board); return 0; } Giving this input: O X__ ___ ___ The algorithm chooses to place a piece at 0, 1, causing a guaranteed loss, do to this trap(nothing can be done to win or end in a draw): XO_ X__ ___ Perhaps it has something to do with the evaluation function? If so, how could I fix it?

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  • Sorting a Linked List [closed]

    - by Mohit Sehgal
    I want to sort a linked list. Here Node is class representing a node in a Linked List I have written a code to bubble sort a linked list. Program does not finishes execution. Kindly point out the mistakes. class Node { public: int data; public: Node *next; Node() { data=0;next=0; } Node(int d) { data=d; } void setData(int d) { data=d; } void print() { cout<<data<<endl; } bool operator==(Node n) { return this->data==n.data; } bool operator >(Node d) { if((this->data) > (d.data)) return true; return false; } }; class LList { public: int noOfNodes; Node *start;/*Header Node*/ LList() { start=new Node; noOfNodes=0;start=0; } void addAtFront(Node* n) { n->next=(start); start=n; noOfNodes++; } void addAtLast(Node* n) { Node *cur=(start); n->next=NULL; if(start==NULL) { start=n; noOfNodes++; return; } while(cur->next!=NULL) { cur=cur->next; } cur->next=n; noOfNodes++; } void addAtPos(Node *n,int pos) { if(pos==1) { addAtFront(n);return; } Node *cur=(start); Node *prev=NULL; int curPos=0; n->next=NULL; while(cur!=NULL) { curPos++; if(pos==curPos+1) { prev=cur; } if(pos==curPos) { n->next=cur; prev->next=n; break; } cur=cur->next; } noOfNodes++; } void removeFirst() { Node *del=start; start=start->next; delete del; noOfNodes--; return; } void removeLast() { Node *cur=start,*prev=NULL; while(cur->next!=NULL) { prev=cur; cur=cur->next; } prev->next=NULL; Node *del=cur->next; delete del; noOfNodes--; return; } void removeNodeAt(int pos) { if(pos<1) return; if(pos==1) { removeFirst();return;} int curPos=1; Node* cur=start->next; Node* prev=start; Node* del=NULL; while(curPos<pos&&cur!=NULL) { curPos++; if(curPos==pos) { del=cur; prev->next=cur->next; cur->next=NULL; delete del; noOfNodes--; break; } prev=prev->next; cur=cur->next; } } void removeNode(Node *d) { Node *cur=start; if(*d==*cur) { removeFirst();return; } cur=start->next; Node *prev=start,*del=NULL; while(cur!=NULL) { if(*cur==*d) { del=cur; prev->next=cur->next; delete del; noOfNodes--; break; } prev=prev->next; cur=cur->next; } } int getPosition(Node data) { int pos=0; Node *cur=(start); while(cur!=NULL) { pos++; if(*cur==data) { return pos; } cur=cur->next; } return -1;//not found } Node getNode(int pos) { if(pos<1) return -1;// not a valid position else if(pos>noOfNodes) return -1; // not a valid position Node *cur=(start); int curPos=0; while(cur!=NULL) { if(++curPos==pos) return *cur; cur=cur->next; } } void reverseList()//reverse the list { Node* cur=start->next; Node* d=NULL; Node* prev=start; while(cur!=NULL) { d=cur->next; cur->next=start; start=cur; prev->next=d; cur=d; } } void sortBubble() { Node *i=start,*j=start,*prev=NULL,*temp=NULL,*after=NULL; int count=noOfNodes-1;int icount=0; while(i->next!=NULL) { j=start; after=j->next; icount=0; while(++icount!=count) { if((*j)>(*after)) { temp=after->next; after->next=j; prev->next=j->next; j->next=temp; prev=after; after=j->next; } else{ prev=j; j=after; after=after->next; } } i=i->next; count--; } } void traverse() { Node *cur=(start); int c=0; while(cur!=NULL) { // cout<<"start"<<start; c++; cur->print(); cur=cur->next; } noOfNodes=c; } ~LList() { delete start; } }; int main() { int n; cin>>n; int d; LList list; Node *node; Node *temp=new Node(2123); for(int i=0;i<n;i++) { cin>>d; node=new Node(d); list.addAtLast(node); } list.addAtPos(temp,1); cout<<"traverse\n"; list.traverse(); temp=new Node(12); list.removeNode(temp); cout<<"12 removed"; list.traverse(); list.reverseList(); cout<<"\nreversed\n"; list.traverse(); cout<<"bubble sort\n"; list.sortBubble(); list.traverse(); getch(); delete node; return 0; }

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