[Haskell-cafe] Re: Referential Transparency and Monads

Eugene Kirpichov 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.

>        Stefan
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Eugene Kirpichov
Web IR developer, market.yandex.ru

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