import java.util.Scanner;

/* ExponentiationTester.java
** Java application for testing a recursive method that raises a given 
** base to a given (integer) power.
**
** Author: R. McCloskey and < lab team members >
** Known defects: ...
*/

public class ExponentiationTester {

   private static Scanner keyboard;
   private static int multCntr;  // keeps track of # multiplications performed
   private static int depth;     // keeps track of depth of recursion


   // Method of interest
   // ------------------

   /* Returns x raised to the n-th power.
   ** Also increases the value of global variable multCntr by the number of
   ** multiplications done here.
   ** pre: n >= 0.
   */
   public static double xToTheNRec(double x, int n) {
      double result;
      if (true)   // replace 'true' by base case condition
         { result = 0; }   // replace '0' by appropriate expression
      else {      // recursive case
         // here goes a block of code that handles the two recursive cases,
         // ultimately assigning the correct number to 'result'.
         result = 0;  
      }
      return result;
   }

   /* Does the same thing as the method above, but narrates its own
   ** execution by printing messages indicating the incoming parameter
   ** values and outgoing result.
   */
   public static double xToTheNRecNarrated(double x, int n) {
      depth = depth + 1;
      println(depth, "Received x:" + x + "; n:" + n);

      double result;
      if (true)   // replace 'true' by base case condition
         { result = 0; }   // replace '0' by appropriate expression
      else {      // recursive case
         // here goes a block of code that handles the two recursive cases,
         // ultimately assigning the correct number to 'result'.
         result = 0;  
      }
      println(depth, "Returning " + result + " having received " +
                     "x:" + x + "; n:" + n);
      depth = depth - 1;
      return result;
   }

   /* Returns the given number squared (and increments multCntr)
   */
   private static double squareOf(double z) {
      multCntr++;
      return z*z;
      // Alternative to line above:
      //   return Math.pow(z,2);
   }




   // Methods supporting the self-narration of xToTheNRecNarrated().
   // --------------------------------------------------------------

   /* Prints the given string, indented in accord with 'depth'.
   */
   private static void print(int depth, String s) {
      printSpaces(3*depth);
      System.out.print(s);
   }

   /* Prints the given string, indented in accord with 'depth'; then
   ** skips to next line.
   */
   private static void println(int depth, String s) {
      print(depth, s);
      System.out.println();
   }

   /* Prints the specified number of spaces.
   */
   private static void printSpaces(int num) {
      for (int i=0; i != num; i++) { System.out.print(' '); }
   }


   // main () method for testing
   // --------------------------

   public static void main(String[] args) {
      final String basePrompt = "Enter a base (real number): ";
      final String exponentPrompt = "Enter an exponent (integer): ";

      keyboard = new Scanner(System.in);

      double base = Double.parseDouble(getResponse(basePrompt).trim());
      int exponent = Integer.parseInt(getResponse(exponentPrompt).trim());

      // Loop terminates when user enters a negative value for the exponent.
      while (exponent >= 0) {
         multCntr = 0;   // reset the multiplication counter to zero
         //double result = xToTheNRec(base, exponent);
         depth = -1;
         double result = xToTheNRecNarrated(base, exponent);
         double correctResult = Math.pow(base,exponent);
         System.out.println("\nYour method produced " + result);
         System.out.println("Math.pow() produced  " + correctResult);

         System.out.println("Your method performed " + multCntr + " multiplications.\n");

         base = Double.parseDouble(getResponse(basePrompt).trim());
         exponent = Integer.parseInt(getResponse(exponentPrompt).trim());
      }
   }

   /* Displays the given prompt and returns the String entered at the keyboard
   ** in response.
   */
   private static String getResponse(String prompt) {
      System.out.print(prompt);
      return keyboard.nextLine();
   }

}