This C++ program defines a class called evalPostFix that evaluates postfix expressions. The class contains methods to push and pop values onto a stack, perform arithmetic operations on values, and a calc method that iterates through a postfix string, pushes operands and pops to evaluate operators, returning the final value. The main function prompts the user to enter a postfix expression, calls the calc method to evaluate it, and outputs the result.

1. #include<iostream>
#include<cctype>
using namespace std;
class evalPostFix
{
public:
int s[50];
int top;
char str[50];
evalPostFix() {
top=-1;
}
void push(int val) {
top++;
s[top]=val;
}
int pop() {
int val=s[top];
top--;
return val;
}
int oper(int x,int y,char op) {
switch(op) {
case '+':return x+y;
case '-':return x-y;
case '*':return x*y;
case '/':return x/y;
default: return 0;
}

2. }
int calc();
};
int evalPostFix::calc() {
int i=0;
while(str[i]!='=') {
if(isdigit(str[i])) {
push(str[i]-'0');
}
else {
int x=pop();
int y=pop();
int r=oper(x,y,str[i]);
push(r);
}
i++;
}
return pop();
}
int main()
{
char answer;
evalPostFix eval;
do
{
cout<<"Enter a postfix expression:" << endl;
cin>>eval.str;
int r=eval.calc();
cout<<"Final Value : "<<r <<"n";
cout << "Continue (Y or N)" << endl;
cin >> answer;
}
while(answer!='N');

3. system("pause");
}
Here is the output, but I do not want it to be like this.
I want the output to be like this