Betr.: [clean-list] IEEE floating point and Clean

[M.Kesseler@aia.nl]

>But Kahan is playing close to his chest and I cannot really figure
>out what he means when he writes that Java has no possibility to
>handle exceptions.

The exceptions that Kahan talks about are not Java-exeptions, but
error conditions like overflow, underflow etc. One way to deal with
this (according to IEEE 754) is to use a special floating-point
value for representing these conditions, AND to use specific rules for
subsequent operations on them.

These rules however are sometimes problematic. See page 23:
"(finite/Overflow) becomes 0 , (NaN < 7) becomes false , ... Perhaps
no traces will be left to arouse suspicions that plausible final
results are actually quite wrong."

So, some computations with exceptional values yield ordinary results.
This can be dangerous. Java provides no built-in way to check that
such a situation has occured. Clean does not either (as far as I know).
If you see 'INF' in your program, that is just a representation of
an exceptional value.

regards,
Marco Kesseler

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