/**
 * File: ReversePolishCalculatorMess 
 * Authors: Wayne Snyder and Leo Reyzin (snyder@cs.bu.edu, reyzin@cs.bu.edu) 
 * Date: 9/20/2011 
 * Purpose: This is a prototype of a program to evaluate postfix ("reverse Polish") expressions; the
 *    assignment is to take this clunky, static code, and turn it into a reasonable object-oriented
 *    program. 
 * Platform: This was developed on Mac OS X 10.6.5 in Dr. Java
 * 
 */

import java.util.Scanner;

public class ReversePolishCalculatorMess {
  
  public static void main(String[] args) {
    
    double V [] = new double[26];
    double S [] = new double[100];
    int next = 0;
    
    Scanner sc = new Scanner(System.in); 
    
    while(sc.hasNext()) {
      
      if (sc.hasNextDouble())
        S[next++] = sc.nextDouble();
      
      else {
        String cmd = sc.next();
        if (cmd.equals("set")) {
          char var = sc.next().charAt(0);
          V[var-'a'] = sc.nextDouble();
        }
        
        else {
          char cmdChar = cmd.charAt(0);
          if (cmdChar>='a' && cmdChar<='z')
            S[next++] = V[cmdChar-'a'];
          else {  
            double op2 = S[--next];
            double op1 = S[--next];
            switch (cmdChar) {
              case '+':
                S[next++] = op1 + op2;
                break;
              case '-':
                S[next++] = op1 - op2;
                break;
              case '/':
                S[next++] = op1 / op2;
                break;
              case '*':
                S[next++] = op1 * op2;
                break;
            }
          }
        }
      }
      System.out.print("Stack: ");
      for (int i=0; i<next; i++) {
        System.out.print(S[i]); 
        System.out.print(" ");
      }
      System.out.print("\n");
    }
  }
}