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  • Classes and Objects in C++

    - by anurag18294
    class anurag { private: int rollno; char name[50]; int marks; float percen; void percentage(int num) { percen=(num/500)*100; } public: void getdata(void) { cout<<"\n\nEnter the name of the student:"; gets(name); cout<<"\n\nEnter the roll no: and the marks:"; cin>>rollno>>marks; percentage(marks); } void display(void) { cout<<"\n\nThe name of the student is:"; cout.write(name,50); cout<<"\n\nThe roll no: of the student is:"; cout<<rollno; cout<<"\n\n The marks obtained is:"<<marks; cout<<"\n\nThe percentage is:"<<percen; }}; void main() { clrscr(); anurag F; F.getdata(); F.display(); getch(); } why the following code is not giving the desired output?

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  • new and delete operator overloading

    - by Angus
    I am writing a simple program to understand the new and delete operator overloading. How is the size parameter passed into the new operator? For reference, here is my code: #include<iostream> #include<stdlib.h> #include<malloc.h> using namespace std; class loc{ private: int longitude,latitude; public: loc(){ longitude = latitude = 0; } loc(int lg,int lt){ longitude -= lg; latitude -= lt; } void show(){ cout << "longitude" << endl; cout << "latitude" << endl; } void* operator new(size_t size); void operator delete(void* p); void* operator new[](size_t size); void operator delete[](void* p); }; void* loc :: operator new(size_t size){ void* p; cout << "In overloaded new" << endl; p = malloc(size); cout << "size :" << size << endl; if(!p){ bad_alloc ba; throw ba; } return p; } void loc :: operator delete(void* p){ cout << "In delete operator" << endl; free(p); } void* loc :: operator new[](size_t size){ void* p; cout << "In overloaded new[]" << endl; p = malloc(size); cout << "size :" << size << endl; if(!p){ bad_alloc ba; throw ba; } return p; } void loc :: operator delete[](void* p){ cout << "In delete operator - array" << endl; free(p); } int main(){ loc *p1,*p2; int i; cout << "sizeof(loc)" << sizeof(loc) << endl; try{ p1 = new loc(10,20); } catch (bad_alloc ba){ cout << "Allocation error for p1" << endl; return 1; } try{ p2 = new loc[10]; } catch(bad_alloc ba){ cout << "Allocation error for p2" << endl; return 1; } p1->show(); for(i = 0;i < 10;i++){ p2[i].show(); } delete p1; delete[] p2; return 0; }

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  • Switch Statement C++ - error C2046: illegal case, error C2043: illegal break

    - by user318095
    #include <iostream> #include <string> using namespace std; //void multiply(int b); int main() { float total = 0; float b = 0; cout << "Enter number: " << endl; cin >> b; char TorD; cout << "Would you like to times (*), divide (/), add (+) or minus (-) this number?" << endl; cin >> TorD; switch (TorD) case '*' : { int c=0; cout << "by how many?" << endl; cin >> c; total = b * c; cout << b << " * " << c << " = " << total << endl; } break; case '/' : { int c=0; cout << "by how many?" << endl; cin >> c; total = b / c; cout << b << " / " << c << " = " << total << endl; } break; case '+' : { int c=0; cout << "by how many?" << endl; cin >> c; total = b + c; cout << b << " + " << c << " = " << total << endl; } break; case '-' : { int c=0; cout << "by how many?" << endl; cin >> c; total = b - c; cout << b << " - " << c << " = " << total << endl; } break; default: cout << "You did not correctly enter /, *, +, or - !!" << endl; //multiply(b); system("pause"); return 0; }

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  • Im getting fatal errors... can anyone help me edit my program!

    - by user350217
    The errors i am getting are: Error 1 error LNK2019: unresolved external symbol "double __cdecl getDollarAmt(void)" (? getDollarAmt@@YANXZ) referenced in function _main hid.obj Error 2 fatal error LNK1120: 1 unresolved externals this is my program: #include<iostream> #include<cmath> #include<string> using namespace std; double getDollarAmt(); void displayCurrencies(); char getCurrencySelection (float amtExchanged); bool isSelectionValid(char selection); double calcExchangeAmt (float amtExchanged, char selection); void displayResults(double newAmount, float amtExchanged, char selection, char yesNo); const double russianRubles = 31.168; const double northKoreanWon = .385; const double chineseYuan = 6.832; const double canadianDollar = 1.1137; const double cubanPeso = 1.0; const double ethiopianBirr = 9.09; const double egyptianPound = 5.6275; const double tunisianDinar = 1.3585; const double thaiBaht = 34.4; /****** I changed the variables to global variables so you don't have to worry about accidentally setting them to 0 or assigning over a value that you need ********/ float amtEchanged = 0.0; char selection; char yesNo; double newAmount; int main() { float amtExchanged = 0.0; selection = 'a'; yesNo = 'y'; newAmount = 0.0; getDollarAmt (); displayCurrencies(); getCurrencySelection (amtExchanged); isSelectionValid(selection);/**** you only need to use the selection variable ****/ calcExchangeAmt (amtExchanged, selection); displayResults(newAmount, amtExchanged, selection, yesNo); return 0; } double getDollarAmt (float amtExchanged) // promt user for eachange amount and return it to main { float amtExchanged0;//created temporary variable to set amtExchanged to cout<< "Please enter the total dollar amount to exchange: "; cin>> amtExchanged0; amtExchanged = amtExchanged0;//setting amtExchanged to the right value return amtExchanged; } void displayCurrencies() // display list of currencies { cout<<"A Russian Ruble"<<endl <<"B North Korean Won"<<endl <<"C Chinese Yuan"<<endl <<"D Cuban Peso"<<endl <<"E Ethiopian Birr"<<endl <<"F Thai Baht"<<endl <<"G Canadian Dollars"<<endl <<"H Tunisian Dinar"<<endl <<"I Egyptian Pound"<<endl; } char getCurrencySelection (float amtExchanged) // make a selection and return to main { char selection0;//again, created a temporary variable for selection cout<<"Please enter your selection: "; cin>>selection0; selection = selection0;//setting the temporary variable to the actual variable you use /***** we are now going to see if isSelectionValid returns false. if it returns false, that means that their selection was not character A-H. if it is false we keep calling getCurrencySelection *****/ if(isSelectionValid(selection)==false) { cout<<"Sorry, the selection you chose is invalid."<<endl; getCurrencySelection(amtExchanged); } return selection; } bool isSelectionValid(char selection) // this fuction is supposed to be called from getCurrencySelection, the selction // must be sent to isSelectionValid to determine if its valid // if selection is valid send it bac to getCurrencySelection // if it is false then it is returned to getCurrencySelection and prompted to // make another selection until the selection is valid, then it is returned to main. { /**** i'm not sure if this is what you mean, all i am doing is making sure that their selection is A-H *****/ if(selection=='A' || selection=='B' || selection=='C' || selection=='D' || selection=='E' || selection=='F' || selection=='G' || selection=='H' || selection=='I') return true; else return false; } double calcExchangeAmt (float amtExchanged,char selection) // function calculates the amount of money to be exchanged { switch (toupper(selection)) { case 'A': newAmount =(russianRubles) * (amtExchanged); break; case 'B': newAmount = (northKoreanWon) * (amtExchanged); break; case 'C': newAmount = (chineseYuan) * (amtExchanged); break; case 'D': newAmount = (canadianDollar) * (amtExchanged); break; case 'E': newAmount = (cubanPeso) * (amtExchanged); break; case 'F': newAmount = (ethiopianBirr) * (amtExchanged); break; case 'G': newAmount = (egyptianPound) * (amtExchanged); break; case 'H': newAmount = (tunisianDinar) * (amtExchanged); break; case 'I': newAmount = (thaiBaht) * (amtExchanged); break; } return newAmount; } void displayResults(double newAmount, float amtExchanged, char selection, char yesNo) // displays results and asked to repeat. IF they want to repeat it clears the screen and starts over. { switch(toupper(selection)) { case 'A': cout<<"$"<<amtExchanged<<" is "<<newAmount<<" Russian Rubles."<<endl<<endl; break; case 'B': cout<<"$"<<amtExchanged<<" is "<<newAmount<<" North Korean Won."<<endl<<endl; break; case 'C': cout<<"$"<<amtExchanged<<" is "<<newAmount<<" Chinese Yuan."<<endl<<endl; break; case 'D': cout<<"$"<<amtExchanged<<" is "<<newAmount<<" Cuban Pesos."<<endl<<endl; break; case 'E': cout<<"$"<<amtExchanged<<" is "<<newAmount<<" Ethiopian Birr."<<endl<<endl; break; case 'F': cout<<"$"<<amtExchanged<<" is "<<newAmount<<" Thai Baht."<<endl<<endl; break; case 'G': cout<<"$"<<amtExchanged<<" is "<<newAmount<<" Canadian Dollars."<<endl<<endl; break; case 'H': cout<<"$"<<amtExchanged<<" is "<<newAmount<<" Tunisian Dinar."<<endl<<endl; break; case 'I': cout<<"$"<<amtExchanged<<" is "<<newAmount<<" Egyptian Pound."<<endl<<endl; break; } cout<<"Do you wish to continue? (Y for Yes / N for No)"; cin>>yesNo; if(yesNo=='y' || yesNo=='Y') { getDollarAmt(); } else { system("cls"); } }

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  • C++ non-member functions for nested template classes

    - by beldaz
    I have been writing several class templates that contain nested iterator classes, for which an equality comparison is required. As I believe is fairly typical, the comparison is performed with a non-member (and non-friend) operator== function. In doing so, my compiler (I'm using Mingw32 GCC 4.4 with flags -O3 -g -Wall) fails to find the function and I have run out of possible reasons. In the rather large block of code below there are three classes: a Base class, a Composed class that holds a Base object, and a Nested class identical to the Composed class except that it is nested within an Outer class. Non-member operator== functions are supplied for each. These classes are in templated and untemplated forms (in their own respective namespaces), with the latter equivalent to the former specialised for unsigned integers. In main, two identical objects for each class are compared. For the untemplated case there is no problem, but for the templated case the compiler fails to find operator==. What's going on? #include <iostream> namespace templated { template<typename T> class Base { T t_; public: explicit Base(const T& t) : t_(t) {} bool equal(const Base& x) const { return x.t_==t_; } }; template<typename T> bool operator==(const Base<T> &x, const Base<T> &y) { return x.equal(y); } template<typename T> class Composed { typedef Base<T> Base_; Base_ base_; public: explicit Composed(const T& t) : base_(t) {} bool equal(const Composed& x) const {return x.base_==base_;} }; template<typename T> bool operator==(const Composed<T> &x, const Composed<T> &y) { return x.equal(y); } template<typename T> class Outer { public: class Nested { typedef Base<T> Base_; Base_ base_; public: explicit Nested(const T& t) : base_(t) {} bool equal(const Nested& x) const {return x.base_==base_;} }; }; template<typename T> bool operator==(const typename Outer<T>::Nested &x, const typename Outer<T>::Nested &y) { return x.equal(y); } } // namespace templated namespace untemplated { class Base { unsigned int t_; public: explicit Base(const unsigned int& t) : t_(t) {} bool equal(const Base& x) const { return x.t_==t_; } }; bool operator==(const Base &x, const Base &y) { return x.equal(y); } class Composed { typedef Base Base_; Base_ base_; public: explicit Composed(const unsigned int& t) : base_(t) {} bool equal(const Composed& x) const {return x.base_==base_;} }; bool operator==(const Composed &x, const Composed &y) { return x.equal(y); } class Outer { public: class Nested { typedef Base Base_; Base_ base_; public: explicit Nested(const unsigned int& t) : base_(t) {} bool equal(const Nested& x) const {return x.base_==base_;} }; }; bool operator==(const Outer::Nested &x, const Outer::Nested &y) { return x.equal(y); } } // namespace untemplated int main() { using std::cout; unsigned int testVal=3; { // No templates first typedef untemplated::Base Base_t; Base_t a(testVal); Base_t b(testVal); cout << "a=b=" << testVal << "\n"; cout << "a==b ? " << (a==b ? "TRUE" : "FALSE") << "\n"; typedef untemplated::Composed Composed_t; Composed_t c(testVal); Composed_t d(testVal); cout << "c=d=" << testVal << "\n"; cout << "c==d ? " << (c==d ? "TRUE" : "FALSE") << "\n"; typedef untemplated::Outer::Nested Nested_t; Nested_t e(testVal); Nested_t f(testVal); cout << "e=f=" << testVal << "\n"; cout << "e==f ? " << (e==f ? "TRUE" : "FALSE") << "\n"; } { // Now with templates typedef templated::Base<unsigned int> Base_t; Base_t a(testVal); Base_t b(testVal); cout << "a=b=" << testVal << "\n"; cout << "a==b ? " << (a==b ? "TRUE" : "FALSE") << "\n"; typedef templated::Composed<unsigned int> Composed_t; Composed_t c(testVal); Composed_t d(testVal); cout << "c=d=" << testVal << "\n"; cout << "d==c ? " << (c==d ? "TRUE" : "FALSE") << "\n"; typedef templated::Outer<unsigned int>::Nested Nested_t; Nested_t e(testVal); Nested_t f(testVal); cout << "e=f=" << testVal << "\n"; cout << "e==f ? " << (e==f ? "TRUE" : "FALSE") << "\n"; // Above line causes compiler error: // error: no match for 'operator==' in 'e == f' } cout << std::endl; return 0; }

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  • what "Debug Assertion Failed" mean and how to fix it, c++?

    - by nonon
    hi, why this program gives me a "Debug Assertion Failed" Error Message while running #include "stdafx.h" #include "iostream" #include "fstream" #include "string" using namespace std; int conv_ch(char b) { int f; f=b; b=b+0; switch(b) { case 48: f=0; break; case 49: f=1; break; case 50: f=2; break; case 51: f=3; break; case 52: f=4; break; case 53: f=5; break; case 54: f=6; break; case 55: f=7; break; case 56: f=8; break; case 57: f=9; break; default: f=0; } return f; } class Student { public: string id; size_t id_len; string first_name; size_t first_len; string last_name; size_t last_len; string phone; size_t phone_len; string grade; size_t grade_len; void print(); void clean(); }; void Student::clean() { id.erase (id.begin()+6, id.end()); first_name.erase (first_name.begin()+15, first_name.end()); last_name.erase (last_name.begin()+15, last_name.end()); phone.erase (phone.begin()+10, phone.end()); grade.erase (grade.begin()+2, grade.end()); } void Student::print() { int i; for(i=0;i<6;i++) { cout<<id[i]; } cout<<endl; for(i=0;i<15;i++) { cout<<first_name[i]; } cout<<endl; for(i=0;i<15;i++) { cout<<last_name[i]; } cout<<endl; for(i=0;i<10;i++) { cout<<phone[i]; } cout<<endl; for(i=0;i<2;i++) { cout<<grade[i]; } cout<<endl; } int main() { Student k[80]; char data[1200]; int length,i,recn=0; int rec_length; int counter = 0; fstream myfile; char x1,x2; char y1,y2; char zz; int ad=0; int ser,j; myfile.open ("example.txt",ios::in); int right; int left; int middle; string key; while(!myfile.eof()){ myfile.get(data,1200); char * pch; pch = strtok (data, "#"); printf ("%s\n", pch); j=0; for(i=0;i<6;i++) { k[recn].id[i]=data[j]; j++; } for(i=0;i<15;i++) { k[recn].first_name[i]=data[j]; j++; } for(i=0;i<15;i++) { k[recn].last_name[i]=data[j]; j++; } for(i=0;i<10;i++) { k[recn].phone[i]=data[j]; j++; } for(i=0;i<2;i++) { k[recn].grade[i]=data[j]; j++; } recn++; j=0; } //cout<<recn; string temp1; size_t temp2; int temp3; for(i=0;i<recn-1;i++) { for(j=0;j<recn-1;j++) { if(k[i].id.compare(k[j].id)<0) { temp1 = k[i].first_name; k[i].first_name = k[j].first_name; k[j].first_name = temp1; temp2 = k[i].first_len; k[i].first_len = k[j].first_len; k[j].first_len = temp2; temp1 = k[i].last_name; k[i].last_name = k[j].last_name; k[j].last_name = temp1; temp2 = k[i].last_len; k[i].last_len = k[j].last_len; k[j].last_len = temp2; temp1 = k[i].grade; k[i].grade = k[j].grade; k[j].grade = temp1; temp2 = k[i].grade_len; k[i].grade_len = k[j].grade_len; k[j].grade_len = temp2; temp1 = k[i].id; k[i].id = k[j].id; k[j].id = temp1; temp2 = k[i].id_len; k[i].id_len = k[j].id_len; k[j].id_len = temp2; temp1 = k[i].phone; k[i].phone = k[j].phone; k[j].phone = temp1; temp2 = k[i].phone_len; k[i].phone_len = k[j].phone_len; k[j].phone_len = temp2; } } } for(i=0;i<recn-1;i++) { k[i].clean(); } char z; string id_sear; cout<<"Enter 1 to display , 2 to search , 3 to exit:"; cin>>z; while(1){ switch(z) { case '1': for(i=0;i<recn-1;i++) { k[i].print(); } break; case '2': cin>>key; right=0; left=recn-2; while(right<=left) { middle=((right+left)/2); if(key.compare(k[middle].id)==0){ cout<<"Founded"<<endl; k[middle].print(); break; } else if(key.compare(k[middle].id)<0) { left=middle-1; } else { right=middle+1; } } break; case '3': exit(0); break; } cout<<"Enter 1 to display , 2 to search , 3 to exit:"; cin>>z; } return 0; } the program reads from a file example.txt 313121crewwe matt 0114323111A # 433444cristinaee john 0113344325A+# 324311matte richee 3040554032B # the idea is to read fixed size field structure with a text seprator record strucutre

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  • Getting template metaprogramming compile-time constants at runtime

    - by GMan - Save the Unicorns
    Background Consider the following: template <unsigned N> struct Fibonacci { enum { value = Fibonacci<N-1>::value + Fibonacci<N-2>::value }; }; template <> struct Fibonacci<1> { enum { value = 1 }; }; template <> struct Fibonacci<0> { enum { value = 0 }; }; This is a common example and we can get the value of a Fibonacci number as a compile-time constant: int main(void) { std::cout << "Fibonacci(15) = "; std::cout << Fibonacci<15>::value; std::cout << std::endl; } But you obviously cannot get the value at runtime: int main(void) { std::srand(static_cast<unsigned>(std::time(0))); // ensure the table exists up to a certain size // (even though the rest of the code won't work) static const unsigned fibbMax = 20; Fibonacci<fibbMax>::value; // get index into sequence unsigned fibb = std::rand() % fibbMax; std::cout << "Fibonacci(" << fibb << ") = "; std::cout << Fibonacci<fibb>::value; std::cout << std::endl; } Because fibb is not a compile-time constant. Question So my question is: What is the best way to peek into this table at run-time? The most obvious solution (and "solution" should be taken lightly), is to have a large switch statement: unsigned fibonacci(unsigned index) { switch (index) { case 0: return Fibonacci<0>::value; case 1: return Fibonacci<1>::value; case 2: return Fibonacci<2>::value; . . . case 20: return Fibonacci<20>::value; default: return fibonacci(index - 1) + fibonacci(index - 2); } } int main(void) { std::srand(static_cast<unsigned>(std::time(0))); static const unsigned fibbMax = 20; // get index into sequence unsigned fibb = std::rand() % fibbMax; std::cout << "Fibonacci(" << fibb << ") = "; std::cout << fibonacci(fibb); std::cout << std::endl; } But now the size of the table is very hard coded and it wouldn't be easy to expand it to say, 40. The only one I came up with that has a similiar method of query is this: template <int TableSize = 40> class FibonacciTable { public: enum { max = TableSize }; static unsigned get(unsigned index) { if (index == TableSize) { return Fibonacci<TableSize>::value; } else { // too far, pass downwards return FibonacciTable<TableSize - 1>::get(index); } } }; template <> class FibonacciTable<0> { public: enum { max = 0 }; static unsigned get(unsigned) { // doesn't matter, no where else to go. // must be 0, or the original value was // not in table return 0; } }; int main(void) { std::srand(static_cast<unsigned>(std::time(0))); // get index into sequence unsigned fibb = std::rand() % FibonacciTable<>::max; std::cout << "Fibonacci(" << fibb << ") = "; std::cout << FibonacciTable<>::get(fibb); std::cout << std::endl; } Which seems to work great. The only two problems I see are: Potentially large call stack, since calculating Fibonacci<2 requires we go through TableMax all the way to 2, and: If the value is outside of the table, it returns zero as opposed to calculating it. So is there something I am missing? It seems there should be a better way to pick out these values at runtime. A template metaprogramming version of a switch statement perhaps, that generates a switch statement up to a certain number? Thanks in advance.

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  • terminate called after throwing an instance of 'std::length_error'

    - by mark
    hello all, this is my first post here. As i am newbie, the problem might be stupid. I was writing a piece of code while the following error message shown, terminate called after throwing an instance of 'std::length_error' what(): basic_string::_S_create /home/gcj/finals /home/gcj/quals where Aborted the following is the offending code especially Line 39 to Line 52. It is weired for me as this block of code is almost same as the Line64 to Line79. int main(){ std::vector<std::string> dirs, need; std::string tmp_str; std::ifstream fp_in("small.in"); std::ofstream fp_out("output"); std::string::iterator iter_substr_begin, iter_substr_end; std::string slash("/"); int T, N, M; fp_in>>T; for (int t = 0; t < T; t++){ std::cout<<" time "<< t << std::endl; fp_in >> N >> M; for (int n =0; n<N; n++){ fp_in>>tmp_str; dirs.push_back(tmp_str); tmp_str.clear(); } for (int m=0; m<M; m++){ fp_in>>tmp_str; need.push_back(tmp_str); tmp_str.clear(); } for (std::vector<std::string>::iterator iter = dirs.begin(); iter!=dirs.end(); iter++){ for (std::string::iterator iter_str = (*iter).begin()+1; iter_str<(*iter).end(); ++iter_str){ if ((*iter_str)=='/') { std::string tmp_str2((*iter).begin(), iter_str); if (find(dirs.begin(), dirs.end(), tmp_str2)==dirs.end()) { dirs.push_back(tmp_str2); } } } } for (std::vector<std::string>::iterator iter_tmp = dirs.begin(); iter_tmp!= dirs.end(); ++iter_tmp) std::cout<<*iter_tmp<<" "; dirs.clear(); std::cout<<std::endl; std::cout<<" need "<<std::endl; //processing the next for (std::vector<std::string>::iterator iter_tmp = need.begin(); iter_tmp!=need.end(); ++iter_tmp) std::cout<<*iter_tmp<<" "; std::cout<<" where "; for (std::vector<std::string>::iterator iter = need.begin(); iter!=need.end(); iter++){ for (std::string::iterator iter_str = (*iter).begin()+1; iter_str<(*iter).end(); ++iter_str){ if ((*iter_str)=='/') { std::string tmp_str2((*iter).begin(), iter_str); if (find(need.begin(), need.end(), tmp_str2)==need.end()) { need.push_back(tmp_str2); } } } } for (std::vector<std::string>::iterator iter_tmp = need.begin(); iter_tmp!= need.end(); ++iter_tmp) std::cout<<*iter_tmp<<" "; need.clear(); std::cout<<std::endl; //finish processing the next } for (std::vector<std::string>::iterator iter= dirs.begin(); iter!=dirs.end(); iter++) std::cout<<*iter<<" "; std::cout<<std::endl; for (std::vector<std::string>::iterator iter= need.begin(); iter!=need.end(); iter++) std::cout<<*iter<<" "; std::cout<<std::endl; fp_out.close(); } best regards, Mark

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  • Repeated Squaring - Matrix Multiplication using NEWMAT

    - by Dinakar Kulkarni
    I'm trying to use the repeated squaring algorithm (using recursion) to perform matrix exponentiation. I've included header files from the NEWMAT library instead of using arrays. The original matrix has elements in the range (-5,5), all numbers being of type float. # include "C:\User\newmat10\newmat.h" # include "C:\User\newmat10\newmatio.h" # include "C:\User\newmat10\newmatap.h" # include <iostream> # include <time.h> # include <ctime> # include <cstdlib> # include <iomanip> using namespace std; Matrix repeated_squaring(Matrix A, int exponent, int n) //Recursive function { A(n,n); IdentityMatrix I(n); if (exponent == 0) //Matrix raised to zero returns an Identity Matrix return I; else { if ( exponent%2 == 1 ) // if exponent is odd return (A * repeated_squaring (A*A, (exponent-1)/2, n)); else //if exponent is even return (A * repeated_squaring( A*A, exponent/2, n)); } } Matrix direct_squaring(Matrix B, int k, int no) //Brute Force Multiplication { B(no,no); Matrix C = B; for (int i = 1; i <= k; i++) C = B*C; return C; } //----Creating a matrix with elements b/w (-5,5)---- float unifRandom() { int a = -5; int b = 5; float temp = (float)((b-a)*( rand()/RAND_MAX) + a); return temp; } Matrix initialize_mat(Matrix H, int ord) { H(ord,ord); for (int y = 1; y <= ord; y++) for(int z = 1; z<= ord; z++) H(y,z) = unifRandom(); return(H); } //--------------------------------------------------- void main() { int exponent, dimension; cout<<"Insert exponent:"<<endl; cin>>exponent; cout<< "Insert dimension:"<<endl; cin>>dimension; cout<<"The number of rows/columns in the square matrix is: "<<dimension<<endl; cout<<"The exponent is: "<<exponent<<endl; Matrix A(dimension,dimension),B(dimension,dimension); Matrix C(dimension,dimension),D(dimension,dimension); B= initialize_mat(A,dimension); cout<<"Initial Matrix: "<<endl; cout<<setw(5)<<setprecision(2)<<B<<endl; //----------------------------------------------------------------------------- cout<<"Repeated Squaring Result: "<<endl; clock_t time_before1 = clock(); C = repeated_squaring (B, exponent , dimension); cout<< setw(5) <<setprecision(2) <<C; clock_t time_after1 = clock(); float diff1 = ((float) time_after1 - (float) time_before1); cout << "It took " << diff1/CLOCKS_PER_SEC << " seconds to complete" << endl<<endl; //--------------------------------------------------------------------------------- cout<<"Direct Squaring Result:"<<endl; clock_t time_before2 = clock(); D = direct_squaring (B, exponent , dimension); cout<<setw(5)<<setprecision(2)<<D; clock_t time_after2 = clock(); float diff2 = ((float) time_after2 - (float) time_before2); cout << "It took " << diff2/CLOCKS_PER_SEC << " seconds to complete" << endl<<endl; } I face the following problems: The random number generator returns only "-5" as each element in the output. The Matrix multiplication yield different results with brute force multiplication and using the repeated squaring algorithm. I'm timing the execution time of my code to compare the times taken by brute force multiplication and by repeated squaring. Could someone please find out what's wrong with the recursion and with the matrix initialization? NOTE: While compiling this program, make sure you've imported the NEWMAT library. Thanks in advance!

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  • Header Guard Issues - Getting Swallowed Alive

    - by gjnave
    I'm totally at wit's end: I can't figure out how my dependency issues. I've read countless posts and blogs and reworked my code so many times that I can't even remember what almost worked and what didnt. I continually get not only redefinition errors, but class not defined errors. I rework the header guards and remove some errors simply to find others. I somehow got everything down to one error but then even that got broke while trying to fix it. Would you please help me figure out the problem? card.cpp #include <iostream> #include <cctype> #include "card.h" using namespace std; // ====DECL====== Card::Card() { abilities = 0; flavorText = 0; keywords = 0; artifact = 0; classType = new char[strlen("Card") + 1]; classType = "Card"; } Card::~Card (){ delete name; delete abilities; delete flavorText; artifact = NULL; } // ------------ Card::Card(const Card & to_copy) { name = new char[strlen(to_copy.name) +1]; // creating dynamic array strcpy(to_copy.name, name); type = to_copy.type; color = to_copy.color; manaCost = to_copy.manaCost; abilities = new char[strlen(to_copy.abilities) +1]; strcpy(abilities, to_copy.abilities); flavorText = new char[strlen(to_copy.flavorText) +1]; strcpy(flavorText, to_copy.flavorText); keywords = new char[strlen(to_copy.keywords) +1]; strcpy(keywords, to_copy.keywords); inPlay = to_copy.inPlay; tapped = to_copy.tapped; enchanted = to_copy.enchanted; cursed = to_copy.cursed; if (to_copy.type != ARTIFACT) artifact = to_copy.artifact; } // ====DECL===== int Card::equipArtifact(Artifact* to_equip){ artifact = to_equip; } Artifact * Card::unequipArtifact(Card * unequip_from){ Artifact * to_remove = artifact; artifact = NULL; return to_remove; // put card in hand or in graveyard } int Card::enchant( Card * to_enchant){ to_enchant->enchanted = true; cout << "enchanted" << endl; } int Card::disenchant( Card * to_disenchant){ to_disenchant->enchanted = false; cout << "Enchantment Removed" << endl; } // ========DECL===== Spell::Spell() { currPower = basePower; currToughness = baseToughness; classType = new char[strlen("Spell") + 1]; classType = "Spell"; } Spell::~Spell(){} // --------------- Spell::Spell(const Spell & to_copy){ currPower = to_copy.currPower; basePower = to_copy.basePower; currToughness = to_copy.currToughness; baseToughness = to_copy.baseToughness; } // ========= int Spell::attack( Spell *& blocker ){ blocker->currToughness -= currPower; currToughness -= blocker->currToughness; } //========== int Spell::counter (Spell *& to_counter){ cout << to_counter->name << " was countered by " << name << endl; } // ============ int Spell::heal (Spell *& to_heal, int amountOfHealth){ to_heal->currToughness += amountOfHealth; } // ------- Creature::Creature(){ summoningSick = true; } // =====DECL====== Land::Land(){ color = NON; classType = new char[strlen("Land") + 1]; classType = "Land"; } // ------ int Land::generateMana(int mana){ // ... // } card.h #ifndef CARD_H #define CARD_H #include <cctype> #include <iostream> #include "conception.h" class Artifact; class Spell; class Card : public Conception { public: Card(); Card(const Card &); ~Card(); protected: char* name; enum CardType { INSTANT, CREATURE, LAND, ENCHANTMENT, ARTIFACT, PLANESWALKER}; enum CardColor { WHITE, BLUE, BLACK, RED, GREEN, NON }; CardType type; CardColor color; int manaCost; char* abilities; char* flavorText; char* keywords; bool inPlay; bool tapped; bool cursed; bool enchanted; Artifact* artifact; virtual int enchant( Card * ); virtual int disenchant (Card * ); virtual int equipArtifact( Artifact* ); virtual Artifact* unequipArtifact(Card * ); }; // ------------ class Spell: public Card { public: Spell(); ~Spell(); Spell(const Spell &); protected: virtual int heal( Spell *&, int ); virtual int attack( Spell *& ); virtual int counter( Spell*& ); int currToughness; int baseToughness; int currPower; int basePower; }; class Land: public Card { public: Land(); ~Land(); protected: virtual int generateMana(int); }; class Forest: public Land { public: Forest(); ~Forest(); protected: int generateMana(); }; class Creature: public Spell { public: Creature(); ~Creature(); protected: bool summoningSick; }; class Sorcery: public Spell { public: Sorcery(); ~Sorcery(); protected: }; #endif conception.h -- this is an "uber class" from which everything derives class Conception{ public: Conception(); ~Conception(); protected: char* classType; }; conception.cpp Conception::Conception{ Conception(){ classType = new char[11]; char = "Conception"; } game.cpp -- this is an incomplete class as of this code #include <iostream> #include <cctype> #include "game.h" #include "player.h" Battlefield::Battlefield(){ card = 0; } Battlefield::~Battlefield(){ delete card; } Battlefield::Battlefield(const Battlefield & to_copy){ } // =========== /* class Game(){ public: Game(); ~Game(); protected: Player** player; // for multiple players Battlefield* root; // for battlefield getPlayerMove(); // ask player what to do addToBattlefield(); removeFromBattlefield(); sendAttack(); } */ #endif game.h #ifndef GAME_H #define GAME_H #include "list.h" class CardList(); class Battlefield : CardList{ public: Battlefield(); ~Battlefield(); protected: Card* card; // make an array }; class Game : Conception{ public: Game(); ~Game(); protected: Player** player; // for multiple players Battlefield* root; // for battlefield getPlayerMove(); // ask player what to do addToBattlefield(); removeFromBattlefield(); sendAttack(); Battlefield* field; }; list.cpp #include <iostream> #include <cctype> #include "list.h" // ========== LinkedList::LinkedList(){ root = new Node; classType = new char[strlen("LinkedList") + 1]; classType = "LinkedList"; }; LinkedList::~LinkedList(){ delete root; } LinkedList::LinkedList(const LinkedList & obj) { // code to copy } // --------- // ========= int LinkedList::delete_all(Node* root){ if (root = 0) return 0; delete_all(root->next); root = 0; } int LinkedList::add( Conception*& is){ if (root == 0){ root = new Node; root->next = 0; } else { Node * curr = root; root = new Node; root->next=curr; root->it = is; } } int LinkedList::remove(Node * root, Node * prev, Conception* is){ if (root = 0) return -1; if (root->it == is){ root->next = root->next; return 0; } remove(root->next, root, is); return 0; } Conception* LinkedList::find(Node*& root, const Conception* is, Conception* holder = NULL) { if (root==0) return NULL; if (root->it == is){ return root-> it; } holder = find(root->next, is); return holder; } Node* LinkedList::goForward(Node * root){ if (root==0) return root; if (root->next == 0) return root; else return root->next; } // ============ Node* LinkedList::goBackward(Node * root){ root = root->prev; } list.h #ifndef LIST_H #define LIST_H #include <iostream> #include "conception.h" class Node : public Conception { public: Node() : next(0), prev(0), it(0) { it = 0; classType = new char[strlen("Node") + 1]; classType = "Node"; }; ~Node(){ delete it; delete next; delete prev; } Node* next; Node* prev; Conception* it; // generic object }; // ---------------------- class LinkedList : public Conception { public: LinkedList(); ~LinkedList(); LinkedList(const LinkedList&); friend bool operator== (Conception& thing_1, Conception& thing_2 ); protected: virtual int delete_all(Node*); virtual int add( Conception*& ); // virtual Conception* find(Node *&, const Conception*, Conception* ); // virtual int remove( Node *, Node *, Conception* ); // removes question with keyword int display_all(node*& ); virtual Node* goForward(Node *); virtual Node* goBackward(Node *); Node* root; // write copy constrcutor }; // ============= class CircularLinkedList : public LinkedList { public: // CircularLinkedList(); // ~CircularLinkedList(); // CircularLinkedList(const CircularLinkedList &); }; class DoubleLinkedList : public LinkedList { public: // DoubleLinkedList(); // ~DoubleLinkedList(); // DoubleLinkedList(const DoubleLinkedList &); protected: }; // END OF LIST Hierarchy #endif player.cpp #include <iostream> #include "player.h" #include "list.h" using namespace std; Library::Library(){ root = 0; } Library::~Library(){ delete card; } // ====DECL========= Player::~Player(){ delete fname; delete lname; delete deck; } Wizard::~Wizard(){ delete mana; delete rootL; delete rootH; } // =====Player====== void Player::changeName(const char[] first, const char[] last){ char* backup1 = new char[strlen(fname) + 1]; strcpy(backup1, fname); char* backup2 = new char[strlen(lname) + 1]; strcpy(backup1, lname); if (first != NULL){ fname = new char[strlen(first) +1]; strcpy(fname, first); } if (last != NULL){ lname = new char[strlen(last) +1]; strcpy(lname, last); } return 0; } // ========== void Player::seeStats(Stats*& to_put){ to_put->wins = stats->wins; to_put->losses = stats->losses; to_put->winRatio = stats->winRatio; } // ---------- void Player::displayDeck(const LinkedList* deck){ } // ================ void CardList::findCard(Node* root, int id, NodeCard*& is){ if (root == NULL) return; if (root->it.id == id){ copyCard(root->it, is); return; } else findCard(root->next, id, is); } // -------- void CardList::deleteAll(Node* root){ if (root == NULL) return; deleteAll(root->next); root->next = NULL; } // --------- void CardList::removeCard(Node* root, int id){ if (root == NULL) return; if (root->id = id){ root->prev->next = root->next; // the prev link of root, looks back to next of prev node, and sets to where root next is pointing } return; } // --------- void CardList::addCard(Card* to_add){ if (!root){ root = new Node; root->next = NULL; root->prev = NULL; root->it = &to_add; return; } else { Node* original = root; root = new Node; root->next = original; root->prev = NULL; original->prev = root; } } // ----------- void CardList::displayAll(Node*& root){ if (root == NULL) return; cout << "Card Name: " << root->it.cardName; cout << " || Type: " << root->it.type << endl; cout << " --------------- " << endl; if (root->classType == "Spell"){ cout << "Base Power: " << root->it.basePower; cout << " || Current Power: " << root->it.currPower << endl; cout << "Base Toughness: " << root->it.baseToughness; cout << " || Current Toughness: " << root->it.currToughness << endl; } cout << "Card Type: " << root->it.currPower; cout << " || Card Color: " << root->it.color << endl; cout << "Mana Cost" << root->it.manaCost << endl; cout << "Keywords: " << root->it.keywords << endl; cout << "Flavor Text: " << root->it.flavorText << endl; cout << " ----- Class Type: " << root->it.classType << " || ID: " << root->it.id << " ----- " << endl; cout << " ******************************************" << endl; cout << endl; // ------- void CardList::copyCard(const Card& to_get, Card& put_to){ put_to.type = to_get.type; put_to.color = to_get.color; put_to.manaCost = to_get.manaCost; put_to.inPlay = to_get.inPlay; put_to.tapped = to_get.tapped; put_to.class = to_get.class; put_to.id = to_get.id; put_to.enchanted = to_get.enchanted; put_to.artifact = to_get.artifact; put_to.class = to_get.class; put.to.abilities = new char[strlen(to_get.abilities) +1]; strcpy(put_to.abilities, to_get.abilities); put.to.keywords = new char[strlen(to_get.keywords) +1]; strcpy(put_to.keywords, to_get.keywords); put.to.flavorText = new char[strlen(to_get.flavorText) +1]; strcpy(put_to.flavorText, to_get.flavorText); if (to_get.class = "Spell"){ put_to.baseToughness = to_get.baseToughness; put_to.basePower = to_get.basePower; put_to.currToughness = to_get.currToughness; put_to.currPower = to_get.currPower; } } // ---------- player.h #ifndef player.h #define player.h #include "list.h" // ============ class CardList() : public LinkedList(){ public: CardList(); ~CardList(); protected: virtual void findCard(Card&); virtual void addCard(Card* ); virtual void removeCard(Node* root, int id); virtual void deleteAll(); virtual void displayAll(); virtual void copyCard(const Conception*, Node*&); Node* root; } // --------- class Library() : public CardList(){ public: Library(); ~Library(); protected: Card* card; int numCards; findCard(Card&); // get Card and fill empty template } // ----------- class Deck() : public CardList(){ public: Deck(); ~Deck(); protected: enum deckColor { WHITE, BLUE, BLACK, RED, GREEN, MIXED }; char* deckName; } // =============== class Mana(int amount) : public Conception { public: Mana() : displayTotal(0), classType(0) { displayTotal = 0; classType = new char[strlen("Mana") + 1]; classType = "Mana"; }; protected: int accrued; void add(); void remove(); int displayTotal(); } inline Mana::add(){ accrued += 1; } inline Mana::remove(){ accrued -= 1; } inline Mana::displayTotal(){ return accrued; } // ================ class Stats() : public Conception { public: friend class Player; friend class Game; Stats() : wins(0), losses(0), winRatio(0) { wins = 0; losses = 0; if ( (wins + losses != 0) winRatio = wins / (wins + losses); else winRatio = 0; classType = new char[strlen("Stats") + 1]; classType = "Stats"; } protected: int wins; int losses; float winRatio; void int getStats(Stats*& ); } // ================== class Player() : public Conception{ public: Player() : wins(0), losses(0), winRatio(0) { fname = NULL; lname = NULL; stats = NULL; CardList = NULL; classType = new char[strlen("Player") + 1]; classType = "Player"; }; ~Player(); Player(const Player & obj); protected: // member variables char* fname; char* lname; Stats stats; // holds previous game statistics CardList* deck[]; // hold multiple decks that player might use - put ll in this private: // member functions void changeName(const char[], const char[]); void shuffleDeck(int); void seeStats(Stats*& ); void displayDeck(int); chooseDeck(); } // -------------------- class Wizard(Card) : public Player(){ public: Wizard() : { mana = NULL; rootL = NULL; rootH = NULL}; ~Wizard(); protected: playCard(const Card &); removeCard(Card &); attackWithCard(Card &); enchantWithCard(Card &); disenchantWithCard(Card &); healWithCard(Card &); equipWithCard(Card &); Mana* mana[]; Library* rootL; // Library Library* rootH; // Hand } #endif

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  • Why does this C++ code result in a segmentation fault?

    - by user69514
    I keep getting a segmentation fault when the readAuthor() method is called. Does anybody know why this happens? I am supposed to use dynamic arrays, I know this would be so easy if I was using static array. #include <iostream> #include <string> #include <cstring> #include <cstdlib> using namespace std; /** declare arrays **/ int* isbnArr = new int[25]; char* authorArr = new char[25]; char* publisherArr = new char[25]; char* titleArr = new char[25]; int* editionArr = new int[25]; int* yearArr = new int[25]; int* pagesArr = new int[25]; float* retailPriceArr = new float[25]; float* discountedPriceArr = new float[25]; int* stockArr = new int[25]; /** function prototypes **/ int readIsbn(); char* readAuthor(); char* readPublisher(); char* readTitle(); int readEdition(); int readYear(); int readPages(); float readMsrp(); float readDiscountedPrice(); int readStockAmount(); void readonebook(int* isbn, char* author, char* title, char* publisher, int* edition, int* year, int* pages, float* msrp, float* discounted, int* inventory); int main() { bool stop = false; //flag when to stop loop int ind = 0; //index for current book while( !stop ){ cout << "Add book: press A: "; cout << "another thing here "; char choice; cin >> choice; if( choice == 'a' || choice == 'A' ){ readonebook(&isbnArr[ind], &authorArr[ind], &titleArr[ind], &publisherArr[ind], &editionArr[ind], &yearArr[ind], &pagesArr[ind], &retailPriceArr[ind], &discountedPriceArr[ind], &stockArr[ind]); test(&authorArr[ind]); ind++; } } return 0; } /** define functions **/ int readIsbn(){ int isbn; cout << "ISBN: "; cin >> isbn; return isbn; } char* readAuthor(){ char* author; cout << "Author: "; cin >> author; return author; } char* readPublisher(){ char* publisher = NULL; cout << "Publisher: "; cin >> publisher; return publisher; } char* readTitle(){ char* title = NULL; cout << "Title: "; cin >> title; return title; } int readEdition(){ int edition; cout << "Edition: "; cin >> edition; return edition; } int readYear(){ int year; cout << "Year: "; cin >> year; return year; } int readPages(){ int pages; cout << "Pages: "; cin >> pages; return pages; } float readMsrp(){ float price; cout << "Retail Price: "; cin >> price; return price; } float readDiscountedPrice(){ float price; cout << "Discounted Price: "; cin >> price; return price; } int readStockAmount(){ int amount; cout << "Stock Amount: "; cin >> amount; return amount; } void readonebook(int* isbn, char* author, char* title, char* publisher, int* edition, int* year, int* pages, float* msrp, float* discounted, int* inventory){ *isbn = readIsbn(); author = readAuthor(); title = readTitle(); publisher = readPublisher(); *edition = readEdition(); *year = readYear(); *pages = readPages(); *msrp = readMsrp(); *discounted = readDiscountedPrice(); *inventory = readStockAmount(); }

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  • c++ setting string attribute value in class is throwing "Access violation reading location"

    - by user259789
    I am having some trouble getting this simple code to work: class CreateUserView { public: CreateUserView(void); ~CreateUserView(void); UserController* controller; void showView(); string name; string lastname; string address; string email; string dateOfBirth; }; All i need is to set these attributes in the implementation with getline(). CreateUserView::CreateUserView(void) { } void CreateUserView::showView() { cout << endl << " New User" << endl; cout << "--------------------------" << endl; cout << " Name\t\t: "; getline(cin, name); cout << " Lastname\t: "; getline(cin, lastname); cout << " Email\t\t: "; getline(cin, email); cout << " ===============================" << endl; cout << " 1. SAVE 2.CHANGE 3.CANCEL" << endl; cout << " ===============================" << endl; cout << " choice: "; int choice; cin >> choice; cin.ignore(); controller->createUser_choice(choice); } I keep getting this "Access violation reading location" error at this line: getline(cin, name); what's the best way of assigning a value to an std::string attribute of a class? even name = "whatever" is throwing that error!! thanks

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  • Pour quelles raisons les entreprises devraient-elles opter pour des solutions libres ? coût, sécurité, ouverture, pérennité des formats ou autres ?

    Pour quelles raisons les entreprises devraient-elles opter pour des solutions libres ? Par mesure de sécurité, pour réduire les coûts ou autres ?Dernièrement, l'actualité IT a été submergée de sujets relatifs aux logiciels libres et propriétaires (actualités que vous pouvez retrouvez sur nos portails). En effet, la part de marché des logiciels propriétaires dans les administrations seraient en régression, aussi lente qu'elle puisse être. Les administrations publiques ne cessent de migrer vers des...

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  • Problem trying to lock framerate at 60 FPS

    - by shad0w
    I've written a simple class to limit the framerate of my current project. But it does not work as it should. Here is the code: void FpsCounter::Process() { deltaTime = static_cast<double>(frameTimer.GetMsecs()); waitTime = 1000.0/fpsLimit - deltaTime; frameTimer.Reset(); if(waitTime <= 0) { std::cout << "error, waittime: " << waitTime << std::endl; } else { SDL_Delay(static_cast<Uint32>(waitTime)); } if(deltaTime == 0) { currFps = -1; } else { currFps = 1000/deltaTime; } std::cout << "--Timings--" << std::endl; std::cout << "Delta: \t" << deltaTime << std::endl; std::cout << "Delay: \t" << waitTime << std::endl; std::cout << "FPS: \t" << currFps << std::endl; std::cout << "-- --" << std::endl; } Timer::Timer() { startMsecs = 0; } Timer::~Timer() { // TODO Auto-generated destructor stub } void Timer::Start() { started = true; paused = false; Reset(); } void Timer::Pause() { if(started && !paused) { paused = true; pausedMsecs = SDL_GetTicks() - startMsecs; } } void Timer::Resume() { if(paused) { paused = false; startMsecs = SDL_GetTicks() - pausedMsecs; pausedMsecs = 0; } } int Timer::GetMsecs() { if(started) { if(paused) { return pausedMsecs; } else { return SDL_GetTicks() - startMsecs; } } return 0; } void Timer::Reset() { startMsecs = SDL_GetTicks(); } The "FpsCounter::Process()" Method is called everytime at the end of my gameloop. I've got the problem that the loop is correctly delayed only every second frame, so it runs one frame delayed at 60 FPS and the next without delay at over 1000 fps. I am searching the error quite a while now, but I do not find it. I hope somebody can point me in the right direction.

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  • How to check if a variable is an integer? [closed]

    - by FyrePlanet
    I'm going through my C++ book and have currently made a working Guess The Number game. The game generates a random number based on current time, has the user input their guess, and then tells them whether it was too high, too low, or the correct number. The game functions fine if you enter a number, but returns 'Too High' if you enter something that is not a number (such as a letter or punctuation). Not only does it return 'too high', but it also continually returns it. I was wondering what I could do to check if the guess, as input by the user, is an integer and if it is not, to return 'Not a number. Guess again.' Here is the code. #include <iostream> #include <cstdlib> #include <ctime> using namespace std; int main() { srand(time(0)); // seed the random number generator int theNumber = rand() % 100 + 1; // random number between 1 and 100 int tries = 0, guess; cout << "\tWelcome to Guess My Number!\n\n"; do { cout << "Enter a guess: "; cin >> guess; ++tries; if (guess > theNumber) cout << "Too high!\n\n"; if (guess < theNumber) cout << "Too low!\n\n"; } while (guess != theNumber); cout << "\nThat's it! You got it in " << tries << " guesses!\n"; cout << "\nPress Enter to exit.\n"; cin.ignore(cin.rdbuf()->in_avail() + 1); return 0; }

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  • STL vector reserve() and copy()

    - by natersoz
    Greetings, I am trying to perform a copy from one vector (vec1) to another vector (vec2) using the following 2 abbreviated lines of code (full test app follows): vec2.reserve( vec1.size() ); copy(vec1.begin(), vec1.end(), vec2.begin()); While the call to vec2 sets the capacity of vector vec2, the copying of data to vec2 seems to not fill in the values from vec1 to vec2. Replacing the copy() function with calls to push_back() works as expected. What am I missing here? Thanks for your help. vectest.cpp test program followed by resulting output follows. Compiler: gcc 3.4.4 on cygwin. Nat /** * vectest.cpp */ #include <iostream> #include <vector> using namespace std; int main() { vector<int> vec1; vector<int> vec2; vec1.push_back(1); vec1.push_back(2); vec1.push_back(3); vec1.push_back(4); vec1.push_back(5); vec1.push_back(6); vec1.push_back(7); vec2.reserve( vec1.size() ); copy(vec1.begin(), vec1.end(), vec2.begin()); cout << "vec1.size() = " << vec1.size() << endl; cout << "vec1.capacity() = " << vec1.capacity() << endl; cout << "vec1: "; for( vector<int>::const_iterator iter = vec1.begin(); iter < vec1.end(); ++iter ) { cout << *iter << " "; } cout << endl; cout << "vec2.size() = " << vec2.size() << endl; cout << "vec2.capacity() = " << vec2.capacity() << endl; cout << "vec2: "; for( vector<int>::const_iterator iter = vec2.begin(); iter < vec2.end(); ++iter ) { cout << *iter << endl; } cout << endl; } output: vec1.size() = 7 vec1.capacity() = 8 vec1: 1 2 3 4 5 6 7 vec2.size() = 0 vec2.capacity() = 7 vec2:

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  • Odd C++ template behaviour with static member vars

    - by jon hanson
    This piece of code is supposed to calculate an approximation to e (i.e. the mathematical constant ~ 2.71828183) at compile-time, using the following approach; e1 = 2 / 1 e2 = (2 * 2 + 1) / (2 * 1) = 5 / 2 = 2.5 e3 = (3 * 5 + 1) / (3 * 2) = 16 / 6 ~ 2.67 e4 = (4 * 16 + 1) / (4 * 6) = 65 / 24 ~ 2.708 ... e(i) = (e(i-1).numer * i + 1) / (e(i-1).denom * i) The computation is returned via the result static member however, after 2 iterations it yields zero instead of the expected value. I've added a static member function f() to compute the same value and that doesn't exhibit the same problem. #include <iostream> #include <iomanip> // Recursive case. template<int ITERS, int NUMERATOR = 2, int DENOMINATOR = 1, int I = 2> struct CalcE { static const double result; static double f () {return CalcE<ITERS, NUMERATOR * I + 1, DENOMINATOR * I, I + 1>::f ();} }; template<int ITERS, int NUMERATOR, int DENOMINATOR, int I> const double CalcE<ITERS, NUMERATOR, DENOMINATOR, I>::result = CalcE<ITERS, NUMERATOR * I + 1, DENOMINATOR * I, I + 1>::result; // Base case. template<int ITERS, int NUMERATOR, int DENOMINATOR> struct CalcE<ITERS, NUMERATOR, DENOMINATOR, ITERS> { static const double result; static double f () {return result;} }; template<int ITERS, int NUMERATOR, int DENOMINATOR> const double CalcE<ITERS, NUMERATOR, DENOMINATOR, ITERS>::result = static_cast<double>(NUMERATOR) / DENOMINATOR; // Test it. int main (int argc, char* argv[]) { std::cout << std::setprecision (8); std::cout << "e2 ~ " << CalcE<2>::result << std::endl; std::cout << "e3 ~ " << CalcE<3>::result << std::endl; std::cout << "e4 ~ " << CalcE<4>::result << std::endl; std::cout << "e5 ~ " << CalcE<5>::result << std::endl; std::cout << std::endl; std::cout << "e2 ~ " << CalcE<2>::f () << std::endl; std::cout << "e3 ~ " << CalcE<3>::f () << std::endl; std::cout << "e4 ~ " << CalcE<4>::f () << std::endl; std::cout << "e5 ~ " << CalcE<5>::f () << std::endl; return 0; } I've tested this with VS 2008 and VS 2010, and get the same results in each case: e2 ~ 2 e3 ~ 2.5 e4 ~ 0 e5 ~ 0 e2 ~ 2 e3 ~ 2.5 e4 ~ 2.6666667 e5 ~ 2.7083333 Why does result not yield the expected values whereas f() does? According to Rotsor's comment below, this does work with GCC, so I guess the question is, am i relying on some type of undefined behaviour with regards to static initialisation order, or is this a bug with Visual Studio?

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  • invalid input by the user

    - by TJL
    hey guys so this is my program, I need to notify the user that if hhe/she enters a letter other than w d b or w that is an invalid request. what ive done so far does this, but when i input a number to the dollars_withdraw or dollars_deposit or account_balance the program will do the transaction but also add the "invalid request" before going back to main loop. how do i change it so the program wont do that for numerical inputs for the withdraw deposit and balance?: // Atm machine.cpp : Defines the entry point for the console application. #include <iostream> #include <string> using namespace std; int main () { char user_request; string user_string; double account_balance, dollars_withdraw, dollars_deposit; account_balance = 5000; while(account_balance >0) { cout << "Would you like to [W]ithdraw, [D]eposit, Check your [b]alance or [Q]uit?" << endl; cin >> user_string; user_request= user_string[0]; if(user_request == 'w' || user_request== 'W') { cout << "How much would you like to withdraw?" << endl; cin >> dollars_withdraw; if (dollars_withdraw > account_balance || dollars_withdraw <0) cout << "Invalid transaction" << endl; else account_balance = account_balance - dollars_withdraw; cout << "Your new balance is $" << account_balance << endl; } if (user_request == 'd' || user_request== 'D') { cout << "How much would you like to deposit?" << endl; cin >> dollars_deposit; if (dollars_deposit <0) cout << "Invalid transaction" << endl; else account_balance= account_balance + dollars_deposit; cout << "Your new balance is $" << account_balance << endl; } if(user_request == 'b' || user_request == 'B') { account_balance= account_balance; cout << "Your available balance is $" << account_balance << endl; } if(user_request == 'q' || user_request == 'Q') break; else cout << "Invalid request " << endl; } cout << "Goodbye" << endl; return 0; }

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  • Write a program for a report derived from the data in the data file JEWELRY. The data is to be input

    - by Taylor
    here is the JEWELRY file 0011 Money_Clip 2.000 50.00 Other 0035 Paperweight 1.625 175.00 Other 0457 Cuff_Bracelet 2.375 150.00 Bracelet 0465 Links_Bracelet 7.125 425.00 Bracelet 0585 Key_Chain 1.325 50.00 Other 0595 Cuff_Links 0.625 525.00 Other 0935 Royale_Pendant 0.625 975.00 Pendant 1092 Bordeaux_Cross 1.625 425.00 Cross 1105 Victory_Medallion 0.875 30.00 Pendant 1111 Marquis_Cross 1.375 70.00 Cross 1160 Christina_Ring 0.500 175.00 Ring 1511 French_Clips 0.687 375.00 Other 1717 Pebble_Pendant 1.250 45.00 Pendant 1725 Folded_Pendant 1.250 45.00 Pendant 1730 Curio_Pendant 1.063 275.00 Pendant this is the program i have used #include <iostream> #include <string> #include <iomanip> #include <fstream> using namespace std; struct productJewelry { string name; double amount; int itemCode; double size; string group; }; int main() { // declare variables ifstream inFile; int count=0; int x=0; productJewelry product[50]; inFile.open("jewelry.txt"); // file must be in same folder if (inFile.fail()) cout << "failed"; cout << fixed << showpoint; // fixed format, two decimal places cout << setprecision(2); while (inFile.peek() != EOF) { // cout << count << " : "; count++; inFile>> product[x].itemCode; inFile>> product[x].name; inFile>> product[x].size; inFile>> product[x].amount; inFile>> product[x].group; // cout << product[x].itemCode << ", " << product[x].name << ", "<< product[x].size << ", " << product[x].amount << endl; x++; if (inFile.peek() == '\n') inFile.ignore(1, '\n'); } inFile.close(); string temp; bool swap; do { swap = false; for (int x=0; x<count;x++) { if (product[x].name>product[x+1].name) { //these 3 lines are to swap elements in array temp=product[x].name; product[x].name=product[x+1].name; product[x+1].name=temp; swap=true; } } } while (swap); for (x=0; x< count; x++) { //cout<< product[x].itemCode<<" "; //cout<< product[x].name <<" "; //cout<< product[x].size <<" "; //cout<< product[x].amount<<" "; //cout<< product[x].group<<" "<<endl; } system("pause"); // to freeze Dev-c++ output screen return 0; } // end main

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  • To copy data from a webpage into an array of structs and sorted by“name” before producing the data.

    - by Taylor
    include include include include using namespace std; struct productJewelry { string name; double amount; int itemCode; double size; string group; }; int main() { // declare variables ifstream inFile; int count=0; int x=0; productJewelry product[50]; inFile.open("jewelry.txt"); // file must be in same folder if (inFile.fail()) cout << "failed"; cout << fixed << showpoint; // fixed format, two decimal places cout << setprecision(2); while (inFile.peek() != EOF) { // cout << count << " : "; count++; inFile product[x].itemCode; inFile product[x].name; inFile product[x].size; inFile product[x].amount; inFile product[x].group; // cout << product[x].itemCode << ", " << product[x].name << ", "<< product[x].size << ", " << product[x].amount << endl; x++; if (inFile.peek() == '\n') inFile.ignore(1, '\n'); } inFile.close(); string temp; bool swap; do { swap = false; for (int x=0; xproduct[x+1].name) { //these 3 lines are to swap elements in array temp=product[x].name; product[x].name=product[x+1].name; product[x+1].name=temp; swap=true; } } } while (swap); for (x=0; x< count; x++) { //cout<< product[x].itemCode<<" "; //cout<< product[x].name <<" "; //cout<< product[x].size <<" "; //cout<< product[x].amount<<" "; //cout<< product[x].group<<" "<<endl; } system("pause"); // to freeze Dev-c++ output screen return 0; } // end main THE FILE THAT NEEDS TO PRINT AND BE SORTED IN ALPHABETICAL ORDER 0011 Money_Clip 2.000 50.00 Other 0035 Paperweight 1.625 175.00 Other 0457 Cuff_Bracelet 2.375 150.00 Bracelet 0465 Links_Bracelet 7.125 425.00 Bracelet 0585 Key_Chain 1.325 50.00 Other 0595 Cuff_Links 0.625 525.00 Other 0935 Royale_Pendant 0.625 975.00 Pendant 1092 Bordeaux_Cross 1.625 425.00 Cross 1105 Victory_Medallion 0.875 30.00 Pendant 1111 Marquis_Cross 1.375 70.00 Cross 1160 Christina_Ring 0.500 175.00 Ring 1511 French_Clips 0.687 375.00 Other 1717 Pebble_Pendant 1.250 45.00 Pendant 1725 Folded_Pendant 1.250 45.00 Pendant 1730 Curio_Pendant 1.063 275.00 Pendant

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  • To copy data from a webpage into an array of structs and sorted by"name" before producing the data.

    - by Taylor
    include include include include using namespace std; struct productJewelry { string name; double amount; int itemCode; double size; string group; }; int main() { // declare variables ifstream inFile; int count=0; int x=0; productJewelry product[50]; inFile.open("jewelry.txt"); // file must be in same folder if (inFile.fail()) cout << "failed"; cout << fixed << showpoint; // fixed format, two decimal places cout << setprecision(2); while (inFile.peek() != EOF) { // cout << count << " : "; count++; inFile product[x].itemCode; inFile product[x].name; inFile product[x].size; inFile product[x].amount; inFile product[x].group; // cout << product[x].itemCode << ", " << product[x].name << ", "<< product[x].size << ", " << product[x].amount << endl; x++; if (inFile.peek() == '\n') inFile.ignore(1, '\n'); } inFile.close(); string temp; bool swap; do { swap = false; for (int x=0; xproduct[x+1].name) { //these 3 lines are to swap elements in array temp=product[x].name; product[x].name=product[x+1].name; product[x+1].name=temp; swap=true; } } } while (swap); for (x=0; x< count; x++) { //cout<< product[x].itemCode<<" "; //cout<< product[x].name <<" "; //cout<< product[x].size <<" "; //cout<< product[x].amount<<" "; //cout<< product[x].group<<" "<<endl; } system("pause"); // to freeze Dev-c++ output screen return 0; } // end main

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  • Pointer arithmetic.

    - by Knowing me knowing you
    Having code: int** a = new int*[2]; a[0] = new int(1); a[1] = new int(2); cout << "a[0] " << a[0] << '\n'; cout << "a[1] " << a[1] << '\n'; cout << "a[2] " << a[2] << '\n'; cout << "a[0] + 1 " << a[0] + 1 << '\n';//WHY THIS ISN'T == a[1] ? cout << "*(a + 1): " << *(a + 1) << '\n'; //WHY THIS IS == a[1] ? cout << "a[0] - a[1] " << static_cast<int>(a[0] - a[1])<< '\n';//WHY THIS IS == 16 not 4? cout << sizeof(int**); Questions are included right next to relevant lines in code.

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  • Calling base class constructor

    - by The Void
    In the program below, is the line Derived(double y): Base(), y_(y) correct/allowed? That is, does it follow ANSI rules? #include <iostream> class Base { public: Base(): x_(0) { std::cout << "Base default constructor called" << std::endl; } Base(int x): x_(x) { std::cout << "Base constructor called with x = " << x << std::endl; } void display() const { std::cout << x_ << std::endl; } protected: int x_; }; class Derived: public Base { public: Derived(): Base(1), y_(1.2) { std::cout << "Derived default constructor called" << std::endl; } Derived(double y): Base(), y_(y) { std::cout << "Derived constructor called with y = " << y << std::endl; } void display() const { std::cout << Base::x_ << ", " << y_ << std::endl; } private: double y_; }; int main() { Base b1; b1.display(); Derived d1; d1.display(); std::cout << std::endl; Base b2(-9); b2.display(); Derived d2(-8.7); d2.display(); return 0; }

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