Re: [Haskell-cafe] Re: Why purely in haskell?

Am Freitag, 11. Januar 2008 11:33 schrieben Sie:

Wolfgang Jeltsch writes:

...

However, the fact that (0 / 0) == (0 / 0) yields False is quite shocking. It doesn’t adhere to any meaningful axiom set for Eq.

Tough luck, but that's how floating point works, and what the numericalists know, and possibly even love (although I have my doubts). Sanitizing this behavior would make Haskell less usable for real-world numerical problems.

The IEEE floating point equivalence test has to yield false when comparing NaN with NaN. Haskell’s (==) has to yield True or undefined when comparing a value with itself. So Haskell’s (==) just has to be different from the IEEE floating point equivalence test. What about providing a separate function for the latter?

As a compromise, what about an option to make NaN (and presumably the infinities) cause an immediate exception? (And, cetero censeo, exceptions for Int overflow as well.)

This would be far better (and far more Haskell-like).

-k

Best wishes, Wolfgang