Were the procedures for handling Null and Null pointers well defined even for C in 1985 when IEEE-754 was standardized?
There's probably no good way to standardize how to fill when values are null or nan. How else could this be solved without adding special cases for NaN?
In a language with type annotations we indicate whether a type is Optional:
def sum(a: float|None, b: Optional[float]) -> None|float :
def sum(a: float|np.nan|None, b: Optional[float|np.nan]) -> None|float|np.nan :
Well each programming language has a "sort" method that sorts arrays. Should this method throw an exception in case of NaN? I think the NaN rules were the wrong decision. Because of these rules, everywhere there are floating point numbers, the libraries have to have special code for NaN, even if they don't care about NaN. Otherwise there might be ugly bugs, like sorting running into endless loops, data loss, etc. But well, it can't be changed now.
The best description of the decision is probably [1], where Stephen Canon (former member of the IEEE-754 committee if I understand correctly) explains the reasoning.
[1] https://stackoverflow.com/questions/1565164/what-is-the-rati...