/*
 * CalcPolonesa.java
 *
 * Created on 13 de Maio de 2006, 16:09
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */


/*
 * CalcPolonesa.java
 *
 * Created on 15 de Maio de 2006, 03:31
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */
package calcpolonesa;

import java.util.Scanner;

/**
 *
 * @author ismael
 */
public class CalcPolonesa {
  
  /** Creates a new instance of CalcPolonesa */
  public CalcPolonesa() {
  }
  /**
   * @param args the command line arguments
   */
  public static void main(String[] args) {
    Stack s = new Stack(10); // Pilha para 2 números.
    Scanner sc = new Scanner(System.in);
    while( true ){
      // leio a entrada retirando os brancos !!!
      System.out.println("Entre [numero | operador]==> ");
      String ent = sc.nextLine(); ent.trim();
      try {
        // verifica se eh operador, operando ou fim
        if( ehFim(ent) ) {
          break;
        } else if( ehOperando(ent) ) {
          s.push(Float.parseFloat(ent));
        } else if( ehOperador(ent) ) {
          switch( ent.charAt(0)) {
            case '+': s.push(s.pop()+s.pop());
            break;
            case '-': s.push(s.pop()-s.pop());
            break;
            case '*': s.push(s.pop()*s.pop());
            break;
            case '/': s.push(s.pop()/s.pop());
            break;            
            case '=': 
            break;            
          }
          System.out.println("resultado = " + s.top());
        }
      } catch( StackException e) {
        System.out.println("==> Erro na manipulacao da pilha: " + e.getMessage());
      } 
    }
    System.out.println("Ate logo ...");
  }
  
  private static boolean ehOperador(String ent) {
    return ent.charAt(0) == '+' ||
           ent.charAt(0) == '-' ||
           ent.charAt(0) == '/' ||
           ent.charAt(0) == '=' ||
           ent.charAt(0) == '*';
  }
  private static boolean ehOperando(String ent) {
    float n;
    try {
      n = Float.parseFloat(ent);
    } catch ( NumberFormatException e ) {
      return false;
    }
    return true;
  }
  private static boolean ehFim(String ent) {
    return ent.charAt(0) == '.' ||
           ent.charAt(0) == 'q' ;
  }
}