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

[Cristian Baboi]

On Fri, 11 Jan 2008 13:29:35 +0200, Wolfgang Jeltsch  
<g9ks157k at acme.softbase.org> wrote:

> 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.

This is a good thing because one can define natural numbers with such sets  
:-)



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