c++ - switch case being used in a do{}while statement causes the GoAgain to not work properly -

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the following code when run fails activate commands in switch statement prevents goagain @ end of } while not work correctly in asking user if want exit before so. goagain() function works correctly , when called in others. tried having run addition outside of case(even though need fix math) , runs. tries run switch statement sets goagain false , terminates. help!

// fractions project.cpp : defines entry point console application. //  #include "stdafx.h" #include <iostream> #include <string>  using namespace std;  //  =================     struct fraction {          int num;         int den; };  // structure fraction //  =====================  //  ================== //  funtion prototypes //  =================================     fraction add(fraction, fraction);     fraction multiply(fraction, fraction);     fraction subtract(fraction, fraction);     fraction divide(fraction, fraction);     void     printfraction(string, fraction);     void     setfraction(fraction&);     bool     goagain(); //  ================================  //  ============     int main() {          {              int choice;             fraction fa, fb, fc;             setfraction(fa);             setfraction(fb);             printfraction("fa", fa);             printfraction("fb", fb);             add(fa, fb);             printfraction("fa", fa);             printfraction("fb", fb);              fc = add(fa, fb);              printfraction("fa + fb ", fc);                  cout << endl << endl << "table of operations" << endl;                 cout << "a -- addition" << endl;                 cout << "b -- subtraction" << endl;                 cout << "c -- multiplication" << endl;                 cout << "d -- division" << endl << endl;                 cout << "enter choice calculation: ";                 cin >> choice;                  switch (choice) // switch function allows user choose calculation execute                 {                 case 'a':                 case 'a':                 {                     add(fa, fb);                     printfraction("fa", fa);                     printfraction("fb", fb);                      fc = add(fa, fb);                      printfraction("fa + fb ", fc);                  }                      break;                 case 'b':                 case 'b': subtract(fa, fb);                     printfraction("fa", fa);                     printfraction("fb", fb);                      fc = subtract(fa, fb);                      printfraction("fa - fb ", fc);                      goagain();                      break;                 case 'c':                 case 'c': multiply(fa, fb);                     printfraction("fa", fa);                     printfraction("fb", fb);                      fc = multiply(fa, fb);                      printfraction("fa x fb ", fc);                      goagain();                      break;                 case 'd':                 case 'd': divide(fa, fb);                     printfraction("fa", fa);                     printfraction("fb", fb);                      fc = divide(fa, fb);                      printfraction("fa / fb ", fc);                      goagain();                      break;                 }         } while (goagain());            return 0;     }// function main() //  ===================  //  ========================================     fraction add(fraction f1, fraction f2) {          int = f1.num, b = f1.den;         int c = f2.num, d = f2.den;         fraction fsum;          fsum.num = a*d + b*c;         fsum.den = b*d;          return fsum;       }// function add() //  ==================  //  ===========================================================     void printfraction(string fractionname, fraction fraction) {          cout << fractionname << " = ";         cout << fraction.num << "/" << fraction.den << endl;      }// function printfraction() //  ============================  //  ======================================     void setfraction(fraction& fraction) {          cout << "enter value numerator please ==> ";         cin >> fraction.num;          {             cout << "enter value denominator please ==> ";             cin >> fraction.den;              if (fraction.den == 0){                 cout << "the denominator cannot zero. " << endl;                 cout << "enter nonzero denominator." << endl;             } //         } while (fraction.den == 0);     }// function setfraction() //  ==========================  //  ========================================     fraction multiply(fraction f1, fraction f2) {          int = f1.num, b = f1.den;         int c = f2.num, d = f2.den;         fraction fsum;          fsum.num = a*d;         fsum.den = b*c;          return fsum;       }// function multiply() //  =======================  //  ===============     bool goagain(){ //  ===============         char answer;          cout << endl << "would try again? (y/n)";         cin >> answer;         cout << endl;         if (answer == 'y' | answer == 'y')             return true;         else             return false;     }// function goagain() //  ======================  //  =============================================     fraction subtract(fraction f1, fraction f2) {          int = f1.num, b = f1.den;         int c = f2.num, d = f2.den;         fraction fsum;          fsum.num = a*d - b*c;         fsum.den = b*d;          return fsum;       }// function subtract() //  =======================  //  ===========================================     fraction divide(fraction f1, fraction f2) {          int = f1.num, b = f1.den;         int c = f2.num, d = f2.den;         fraction fsum;          fsum.num = (a*d) / (b*c);         fsum.den = b*d;          return fsum;       }// function divide() //  =====================

the variable choice integer, treat character.

that mean when do

cin >> choice

then input function expects integer, , when sees not integer fail, , set choice zero.

if want read character, choice have char. note lead other problems, cin >> choice read single character, , leave newline in input buffer, , need ignore rest of line.

you should add default case switch statement, detect when user inputs did not expect.

you should not call goagain in cases.


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