Hi all !
Well, some of calculations with _ and __ which have valid results seem
OK, some seem questionable.
We don't know if these numbers really mean infinity or if they mean
overflow. Calculations following the overflow can then mean the correct
value is anything. Then we still see them as infinity or negative
infinity and calculate with them as such. Can we even know if their
correct value is positive or negative? I think not. This means we should
only allow calculations with them to result in a valid number if these
calculations would give this valid number regardless of the correct
value of the infinite number.
The fact that a zero can also have a correct value of anything after an
underflow and consecutive operations further complicates the situation?
I think we should at least be able to optionally trap the exceptions.
Cheers,
Erling
Den 2017-09-21 kl. 12:41, skrev Erling Hellenäs:
Hi all !
As I see it letting calculations with _ and __ return a zero means you
risk getting random results. I question if this is really an improvement.
If you can not force an exception instead of a loss of precision you
risk getting random results? These exceptions are a compulsory part of
the standard for a reason?
Cheers,
Erling
Den 2017-09-20 kl. 23:22, skrev Henry Rich:
No; see
http://code.jsoftware.com/wiki/Vocabulary/under Details
http://code.jsoftware.com/wiki/Vocabulary/percent#dyadic Details
It would perhaps be better if 0 * _5 gave -0, but it doesn't. The other
deviations are improvements added by J.
Henry Rich
On Wed, Sep 20, 2017 at 10:51 AM, Erling Hellenäs
<[email protected]>
wrote:
Hi all !
Here is part of the standard. Required exception handling. Things I
discuss in my post. Is it implemented in J?
https://en.wikipedia.org/wiki/
IEEE_754#Exception_handling
The floating point standard is obviously used in environments where the
users can not afford random results, so there must be solutions to the
problems I mention, which we also can see in this wikipedia article.
Cheers,
Erling
Den 2017-09-20 kl. 16:27, skrev Erling Hellenäs:
I hope others want to read my post even if Raul discards it as not
worthy
of comments. /Erling
Den 2017-09-20 kl. 12:25, skrev Raul Miller:
This isn't just J - this is the IEEE-754 floating point standard.
It would be really nice if computers could deal with infinities,
instantly, at no cost. Sadly, though, that's not going to happen.
FYI,
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