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Re: reading NaNs



Aubrey Jaffer <agj@xxxxxxxxxxxx> writes:

>  | >   An implementation may report a violation of an implementation
>  | >   restriction in any calculation for which the result would be
>  | >   0/0.
>  | 
>  | It's not compatible with IEEE-754 because it doesn't guarantee
>  | that by default operations like (/ 0.0 0.0) produce NaN.
>
> Aren't there IEEE-754 modes which throw an exception rather than
> returning NaN?

There are, there are useful too, but they must be explicitly turned
on. So the above description is good as long as "may" means that the
programmer chooses the behavior.

> If the hardware returns a NaN, what the Scheme implementation does
> with the NaN is not within the scope of IEEE-754.

I disagree. IEEE-754 specifies the language-independent interface,
as seem from the point of view of the programmer.

-- 
   __("<         Marcin Kowalczyk
   \__/       qrczak@xxxxxxxxxx
    ^^     http://qrnik.knm.org.pl/~qrczak/