import java.io.*;
import java.util.*;

/**
 * Class: TableExample3.
 * <br>Description: This example illustrates how to use
 * the  buildFromInfix and evaluate methods in the ExprEvaluator class to
 * process parametric functions.  This example uses setT to set the
 * value of t.
 * <p>
 * The output is printed in a table which could be used to create
 * graph.
 * <p>
 * Sample input:
 * <br> Enter the first value for t: 1
 * <br> Enter the last value for t: 4
 * <br> Enter the expression for x: t^2
 * <br> Enter the expression for y: t^3
 * <p>
 * If more than 2 functions are processed, it many be convenient to
 * create arrays for y, expr, and tree and use a loop to process them.
 * <p>Readers may notice that this class is a very simple variation of
 * TableExample2.
 *
 * <p>
 * <b>Requires:</b>
 * <br>ExprEvaluator.java
 * <br>EasyFormat.java
 * <br>DoubleScanner.java
 * @version Date: 6/18/2008
 * @author James Brink, brinkje@plu.edu
 */
public class TableExample3 {

   double t, x, y;
   String exprX, exprY;
   ExprTree treeX, treeY;
   ExprEvaluator evaluator = new ExprEvaluator();
   Scanner scan = new Scanner(System.in);

   /**
    * Constructor for TableExample3.  Calulates x = f(t) and y = g(t) for
    * functions f(x) and g(x) input by the user.  Prints results in a table.
    */
   public TableExample3() {
      double firstT, lastT;
      int exprXLength, exprYLength;
      // get input
      System.out.print("Enter the first value for t: ");
      firstT = scan.nextDouble();
      System.out.print("Enter the last value for t: ");
      lastT = scan.nextDouble();
      scan.nextLine();   //  read and ignore rest of line
      System.out.print("Enter the expression for x: ");
      exprX = scan.nextLine();
      System.out.print("Enter the expression for y: ");
      exprY = scan.nextLine();

      try {
         // determine formatting and print column headings
         exprXLength = Math.max(("  x = " + exprX).length() + 1, 12);
         exprYLength = Math.max(("  y = " + exprY).length() + 1, 12);
         System.out.println(
              "\n" + EasyFormat.format("t", 10)
                   + EasyFormat.format("x = " + exprX, exprXLength)
                   + EasyFormat.format("y = " + exprY, exprYLength));
         // form the expression trees for each expression
         treeX = evaluator.buildFromInfix(exprX);
         treeY = evaluator.buildFromInfix(exprY);
         // evaluate expression at several points and print the results
         t = firstT;
         while (t <=lastT + .05) {
            evaluator.setT(t);
            x = evaluator.evaluate(treeX);
            y = evaluator.evaluate(treeY);
            System.out.println(
              EasyFormat.format(t, 10, 1)
                   + EasyFormat.format(x, exprXLength, 3)
                   + EasyFormat.format(y, exprYLength, 3));
            t = t + .2;

         }
      } catch (Exception e) {
         System.out.println ("Error:  namely: " + e);
      }
   }  // constructor TableExample3

   /**
    * Trivial main program that starts the application.
    */
   public static void main (String args[]) {
      TableExample3 app = new TableExample3();
      System.exit(0);
   }  // end main

} // class TableExample3