c++ - Trying to write a program which analyzes a mathimatical equation, convert to postfix notation and then solves it? -

so first half works fine , great job of converting equation postfix notation after that, command prompt sits there blinking. want convert postfix , solve equation.can on i'm doing wrong? thanks!

#include <iostream> #include <stack> #include <string> #include <sstream> using namespace std;  int priority(string item) //prioritizing operators {     if(item == "(" || item == ")")     {         return 0;     }     else if(item == "+" || item == "-")     {         return 1;     }     else     {         return 2;     } } int main() {     stack <string> mystack; // initializing stack.     stack <int> mynewstack; //used part 2     char line[256];     char line2[256];     cin.getline( line, 256); // , proceeding line input.     string exp = line;     string item;     string postitem; //used part 2     string postfix; //used part 2      istringstream iss(exp);      iss >> item;      while(iss)     {         if(item != "+" && item != "-" && item != "/" && item != "*" && item != "(" && item != ")") //if char number         {             cout << item;             postfix = postfix + item;         }         else if(mystack.size() == 0) // if stack empty         {             mystack.push(item);         }         else if( item == "+" || item == "-" || item == "/" || item == "*") //if char operator         {             if(priority(mystack.top()) < priority(item)) // item on stack greater priority array item             {                 mystack.push(item);             }             else             {                 while(mystack.size() > 0 && priority(mystack.top()) >= priority(item)) //while stack contains something, , item on                 {                     cout << mystack.top();                     postfix = postfix + mystack.top();                     mystack.pop();                 }                 mystack.push(item);             }         }         else if(item == "(") // left peren         {             mystack.push(item);         }         else if(item == ")") // right peren         {             while(mystack.top() != "(")             {                 cout << mystack.top();                 postfix = postfix + mystack.top();                 mystack.pop();              }             mystack.pop();         }         iss >> item;     }     while (mystack.size() > 0 ) //when nothing left evaluate     {         cout << mystack.top();         postfix = postfix + mystack.top();         mystack.pop();     }      //part 2      int x1;     int x2;     int x3;      istringstream iss2(postfix);      iss2 >> postitem;      while(iss2)     {         if(postitem != "+" && postitem != "-" && postitem != "/" && postitem != "*") //if number         {             int n;             n = atoi(postitem.c_str());             mynewstack.push(n);         }         else if( postitem == "+" || postitem == "-" || postitem == "/" || postitem == "*") //if operator         {             if(postitem == "+")             {                 x1 = mynewstack.top();                 mynewstack.pop();                 x2 = mynewstack.top();                 mynewstack.pop();                 x3 = x1 + x2;                 mynewstack.push(x3);             }             else if(postitem == "-")             {                 x1 = mynewstack.top();                 mynewstack.pop();                 x2 = mynewstack.top();                 mynewstack.pop();                 x3 = x1 - x2;                 mynewstack.push(x3);             }             else if(postitem == "/")             {                 x1 = mynewstack.top();                 mynewstack.pop();                 x2 = mynewstack.top();                 mynewstack.pop();                 x3 = x1 * x2;                 mynewstack.push(x3);             }             else if(postitem == "*")             {                 x1 = mynewstack.top();                 mynewstack.pop();                 x2 = mynewstack.top();                 mynewstack.pop();                 x3 = x1 / x2;                 mynewstack.push(x3);             }              iss2 >> postitem;         }     }     cout << "the conversion infix notation is" + mynewstack.top() << endl; } 

go link, click "code related lecture" on bottom , show examples. cant write code here, long. http://sci.notbc.org/~weiss/cisc3130/lectures/04-3-applications-expressionevaluation.html