function arrayProd(array, begin, end) {
	  if (begin == null) {
	    begin = 0;
	  }

	  if (end == null) {
	    end = array.length;
	  }

	  var prod = 1;

	  for (var i = begin; i < end; ++i) {
	    prod *= array[i];
	  }

	  return prod;
	}
Calculate the product of an array of numbers.
@param array The array to calculate the product over.
@param begin Beginning index, inclusive.
@param end Ending index, exclusive.
@return The product.