[Haskell-cafe] Re: Referential Transparency and Monads
ekirpichov at gmail.com
Fri Apr 10 03:33:58 EDT 2009
2009/4/10 Stefan Monnier <monnier at iro.umontreal.ca>:
>>>>> IO a ~ World -> (a, World)
>>>> I still don't understand this; we are passing a World and getting a
>>>> World back,
>>> We are? Why do you think that?
>> Because that's what (World -> (a,World)) means, last I checked.
> No: Hasekll functions are partial, which means that "a -> b" means
> "takes an object of type `a' and if it terminates, it returns an object
> of type `b'". Note the "if it terminates".
> Since neither loop nor loop' terminate, their return type is
> actually meaningless.
Why? They both return _|_, which is a quite legal value of that type.
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