 There are differences of opinion about the proper definition for the result of a numeric function that receives a quiet NaN as input.One view is that the NaN should propagate to the output of the function in all cases to propagate the indication of an error.Another view, and the one taken by the ISO C99 and IEEE 754-2008 standards in general, is that if the function has multiple arguments and the output is uniquely determined by all the non-NaN inputs (including infinity), then that value should be the result.