[Haskell-cafe] Re: what is inverse of mzero and return?
daniel.is.fischer at web.de
Mon Jan 24 18:30:10 EST 2005
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
> 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
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