package step7;
import java.util.List;
import step7.expr.yyLex;
/** output {@link expr} tree in postfix notation.
  */
public class traverse {
  /** postorder traversal to output.
    */
  public void visit (Object node) {
    if (node instanceof Number)
      System.out.print(" "+node);
    else if (node instanceof List) {
      for (int n = 0; n < ((List)node).size(); ++ n)
        visit(((List)node).get(n));
      System.out.print(" "+classname(node));
    }
  }
  /** return last component of (inner) classname.
    */
  protected static String classname (Object obj) {
    String name = obj.getClass().getName();
    return name.substring(name.lastIndexOf("$")+1);
  }
  /** read an expression from standard input and output it in postorder.
    */
  public static void main (String[] args) throws Exception {
    new traverse().visit(new expr().yyparse(new yyLex(System.in)));
    System.out.println();
  }
}