converting postfix to prefix

// CPP Program to convert postfix to prefix 
#include <iostream> 
#include <stack> 
using namespace std; 
  
// function to check if character is operator or not 
bool isOperator(char x) 
{ 
    switch (x) { 
    case '+': 
    case '-': 
    case '/': 
    case '*': 
        return true; 
    } 
    return false; 
} 
  
// Convert postfix to Prefix expression 
string postToPre(string post_exp) 
{ 
    stack<string> s; 
  
    // length of expression 
    int length = post_exp.size(); 
  
    // reading from right to left 
    for (int i = 0; i < length; i++) { 
  
        // check if symbol is operator 
        if (isOperator(post_exp[i])) { 
  
            // pop two operands from stack 
            string op1 = s.top(); 
            s.pop(); 
            string op2 = s.top(); 
            s.pop(); 
  
            // concat the operands and operator 
            string temp = post_exp[i] + op2 + op1; 
  
            // Push string temp back to stack 
            s.push(temp); 
        } 
  
        // if symbol is an operand 
        else { 
  
            // push the operand to the stack 
            s.push(string(1, post_exp[i])); 
        } 
    } 
  
    // stack[0] contains the Prefix expression 
    return s.top(); 
} 
  
// Driver Code 
int main() 
{ 
    string post_exp = "ABC/-AK/L-*"; 
    cout << "Prefix : " << postToPre(post_exp); 
    return 0; 
}