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List:       haskell-cafe
Subject:    Re: [Haskell-cafe] Re: what is inverse of mzero and return?
From:       Daniel Fischer <daniel.is.fischer () web ! de>
Date:       2005-01-24 23:30:10
Message-ID: 200501250030.10819.daniel.is.fischer () web ! de
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Am Montag, 24. Januar 2005 22:59 schrieb Benjamin Franksen:
> Both are wrong. 'just the result matters' is the correct POV for functions,
> but not for IO actions. 'everything matters' is wrong even for IO actions,
> because the actual value returned when the action is executed is completely
> irrelevant to the IO action's identity.

Now that I cannot swallow, that would mean
return 4 == return 5.
I suppose you didn't mean that, though.
Maybe, the internal workings are irrelevant, only visible side-effects and the 
returned value? But which side-effects are relevant?

> And also some of the electrons on transistor 19348587434 on the CPU chip
> move with a slightly reduced velocity due to the computer user shouting
> curses at his machine...

could that alter the number of reductions? 
>
> Seriously, the model in which the 'sameness' resp. identity of IO actions
> is defined takes into account only (a subset of all) externally observable
> effects, not the way a certain interpreter/compiler executes the action
> internally.
>
> I'll stop here; think I have made my point

Yes, and I still don't know which effects do count and why these and not 
others.
>
> Ben
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