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

Cristian Baboi cristi at ot.onrc.ro
Fri Jan 11 07:37:40 EST 2008


On Fri, 11 Jan 2008 14:21:45 +0200, <jerzy.karczmarczuk at info.unicaen.fr>  
wrote:

> Ketil Malde:
>> Wolfgang Jeltsch:
>>> 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.
>>
>> 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.)
>
> People, you are monsters.
> First, despite the *common, well known* truth that Haskell is not
> Mathematics, this illusion seems to be extremely persistent! Haskell is
> a victim -
> no, some users are victims of its success as a formal language, not just
> as a coding tool... They *want* to have Eq as they imagine the equality,
> including the comparison between incomparable. This is BTW a long  
> standing
> philosophical problem. For centuries some speculative guys tried to  
> analyse
> such "assertions" as God == God, or death==death. Or myself==myself.
> Of course, even if they produced some cute conclusions, they had no
> whatsoever sense for the others. Now we have the modern variants of it:
> NaN == NaN, bottom == bottom ...

Well, Haskell has this "referential transparency" thing which say that a  
function is a function and you will never be able to build anything else  
:-)





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