public class Fibonacci {
  
  // ------------------------------------------------------------------------------
  // Fibonacci function, "the rabbit counting function"
  
  public static int fib (int n) {
    if (n <= 1) {
      return n;
    } else {
      return fib(n-1) + fib(n-2);
    }
  }
  
    public static int fibPrint (int n) {
    System.out.println("Entering fib(" + n + ")");
    if (n <= 1) {
      System.out.println("Exiting fib(" + n + ") -> " + n);
      return n;
    } else {
      int result = fibPrint(n-1) + fibPrint(n-2);
      System.out.println("Exiting fib(" + n + ") -> " + result);
      return result;
    }
  }
  
  public static int fibIter (int n) {
    if (n == 0) {
      return 0;
    } else {
      return fibTail(n, 1, 0, 1); 
    }
  }
  
  public static int fibTail (int n, int i, int fibIMinus1, int fibI) {
    if (n == i) {
      return fibI;
    } else {
      return fibTail(n, i+1, fibI, fibI + fibIMinus1);
    }
  }  
  
   public static int fibIterPrint (int n) {
    if (n == 0) {
      return 0;
    } else {
      return fibTailPrint(n, 1, 0, 1); 
    }
  }
  
  public static int fibTailPrint (int n, int i, int fibIMinus1, int fibI) {
    System.out.println("Entering fibTail(" + n + "," + i + 
                                         "," + fibIMinus1 + "," + fibI + ")");

    if (n == i) {
      System.out.println("Exiting fibTail(" + n + "," + i + 
                         "," + fibIMinus1 + "," + fibI + ") -> " + fibI);
      return fibI;
    } else {
      return fibTailPrint(n, i+1, fibI, fibI + fibIMinus1);
    }
  }  
  
  public static void main(String [] args) {
    if (args.length != 2) {
      System.out.println("Usage:  java Fib fib n");
      System.exit(-1);
    }
    int n = Integer.parseInt(args[1]);
    if (args[0].equals("fib"))
      System.out.println("fib(" + n + ") => " + fib(n));
    else if (args[0].equals("fibPrint"))
      System.out.println("fibPrint(" + n + ") => " + fibPrint(n));
    else if (args[0].equals("fibIter"))
      System.out.println("fibIter(" + n + ") => " + fibIter(n));
    else if (args[0].equals("fibIterPrint"))
      System.out.println("fibIterPrint(" + n + ") => " + fibIterPrint(n));
    
    else
      System.out.println("Unrecogized fibonacci version: " + args[0]);
  }
  
}