// **** Imports ****
import java.io.*;
import java.util.*;

/** 
 * Class: TrivialExample5.
 * <br>Description: This trivial examples illustrates how to use
 * the  toPrefix(), toInfix(), and toPostfix() mehods.  It uses
 * loop to allow texting multiple expressions.  Expressions are
 * input in infix and then output in all three methods.
 * This example uses the getValueOf(var, value), setValueOf(var),
 * buildFromInfix and evaluate() methods.  The expression is also
 * evaluated.
 * 
 *<p>
 * To evaluate prefix or postfix expressions, simply replace "buildFromInfix" by
 * "buildFromPrefix" or "buildFromPostfix".
 * <p>
 * <b>Requires:</b>
 * <br>ExprEvaluator.java
 * <br>EasyFormat.java
 * <br>DoubleScanner.java
 * @version Date: 6/10/2008
 * @author James Brink, brinkje@plu.edu
 */
public class TrivialExample5 {

   double valA, valX, valY;
   double infixVal;
   String infix;
   ExprEvaluator evaluator = new ExprEvaluator();
   Scanner scan = new Scanner(System.in);

   /**
    * Constructor for TrivialExample5.
    *
    * Note:  in this case, the expression only uses variables a, x and y.  The
    * values are passed one at time using setValueOf and then the 0 parameter 
    * version of evaluate is used.
    */
   public TrivialExample5() {
      // get input
      System.out.print("Enter the value for a: ");
      valA = scan.nextDouble();
      System.out.print("Enter the value for x: ");
      valX = scan.nextDouble();
      System.out.print("Enter the value for y: ");
      valY = scan.nextDouble();
      scan.nextLine();   //  read rest of line
      while (true) {
         System.out.print("Enter the expression to be evaluated (or press entrer to quit): ");
         infix = scan.nextLine();
         if (infix.trim().equals(""))
            break;
         // evaluate expression and print the results
         try {
            evaluator.setValueOf('a', valA);
            evaluator.setValueOf('x', valX);
            evaluator.setValueOf('y', valY);
            evaluator.buildFromInfix(infix);
            System.out.println("The results are");
            infixVal = evaluator.evaluate();
            System.out.println("a = " + evaluator.getValueOf('a')
                                      + ", x = " +  evaluator.getValueOf('x')
                                      + ", y = " +  evaluator.getValueOf('y')
                                      + ", expression = " + infixVal);
            System.out.println("\nThe expression converted to prefix: " + evaluator.toPrefix());
            System.out.println("The expression converted to postfix: " + evaluator.toPostfix());
            System.out.println("The fully parenthesized infix expression: " + evaluator.toInfix());
                                       
         }catch (Exception e) {
            System.out.println ("Error:  namely: " + e);
         }
      }
   }  // constructor TrivialExample5

   /**
    * Trivial main program that starts the application.
    */
   public static void main (String args[]) {
      TrivialExample5 app = new TrivialExample5();
      System.exit(0);
   }  // end main

} // class TrivialExample5