// Copyright (c) 2012 Sutoiku, Inc. (MIT License)

function DELTA(number1, number2) {
  // Set number2 to zero if undefined
  number2 = (typeof number2 === 'undefined') ? 0 : number2;

  // Return error if either number is not a number
  if (isNaN(number1) || isNaN(number2)) return '#VALUE!';

  // Return delta
  return (number1 === number2) ? 1 : 0;
}