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

Wolfgang Jeltsch g9ks157k at acme.softbase.org
Fri Jan 11 06:29:35 EST 2008

Am Freitag, 11. Januar 2008 10:54 schrieb Wilhelm B. Kloke:
> Wolfgang Jeltsch <g9ks157k at acme.softbase.org> schrieb:
> > However, the fact that (0 / 0) == (0 / 0) yields False is quite shocking.
> >  It doesn?t adhere to any meaningful axiom set for Eq.  So I think that
> > this behavior should be changed.  Think of a set implementation which
> > uses (==) to compare set elements for equality.  The NaN behavior would
> > break this implementation since it would allow for sets which contain NaN
> > multiple times.
> You forget, that the intention of NaN is denial of membership of any set of
> numbers.

This doesn’t matter.  The Set data type I’m talking about would not know about 
NaN and would therefore allow multiple NaNs in a set.

Best wishes,

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