/* File: division.cpp
 * Author: Jason Charney (jrcharneyATgmailDOTcom)
 * Date: Mar 24, 2012
 * Info: Demonstrate the division algorithm
 * LICENSE: MIT!
 * DON'T STEAL! I'll know if you've copied off of me!
 */
#include <iostream>

double p = 0.0000000001;	// precision

class DivideByZero
{
 public:
  double divisor;
  DivideByZero(double x);
};

DivideByZero::DivideByZero(double x) : divisor(x) {}

// x = 1/D
double reciprocal(double d){
 if(d == 0.0) throw DivideByZero(d); 
 double y, z;
 double x = 0.1;		// initial guess
 do{
  y=x*(2.0-d*x);		// x_{i+1} = x_i * (2 - d * x_i)
  if(y == 0.0) break;		// exit the loop if y = 0, x_i is the answer
  std::cout << y << "\t";	// show x_i
  z = y-x;			// dx = x_{i+1} - x_i
  std::cout << z << "\n";	// show dx (optional, but I'm showing it anyway)
  if( z &lt; 0.0)			// if dx &lt; 0
  {
   x = x*0.1;			// x_i = x_i * 0.1
   z = 1.0;			// tell the loop to keep going
  }
  else
   x = y;			// else x_i = x_{i+1}
 }while(z > p);			// do this so as long as dx &gt; p
 return x;			// return x_i
};

// Q = N / D = N * x where x = 1/D
double divide(double n, double d){
 if(n == 0.0) return 0.0;
 if(d == 0.0) throw DivideByZero(d);
 return n * reciprocal(d);
};

int main(){
 try{
  double n, d;
  std::cout << "Enter N: ";
  std::cin  >> n;
  std::cout << "Enter D: ";
  std::cin  >> d;
  std::cout << divide(n,d) << std::endl;	// display the quotient
 }
 catch(DivideByZero divZero){
  std::cerr << "ERROR: DIVBYZERO" << std::endl;
  return -1;
 }
 return 0;
};