[Haskell-cafe] On the purity of Haskell

Jerzy Karczmarczuk jerzy.karczmarczuk at unicaen.fr
Mon Jan 2 11:03:23 CET 2012

Conal Elliott cites Steve Horne:
>     I look at this World parameter as purely hypothetical, a trick
>     used to gain an intuition. Whereas Jerzy (I think) uses it to
>     claim Haskell is referentially transparent - those differing x and
>     y values come from different worlds, or different world-states.
> I don't see this interpretation in Jerzy's words, and I'd be very 
> surprised if he had that sort of argument in mind.
I don't think either having used the 'World' model as an argument of the 
referential transparency.
The main reason is that I don't know what does it mean, the referential 
transparency of the real world.

There is a philosophical issue involved: the problem of IDENTITY, which 
is as old as the humanity, and it will survive it... We simply don't 
know what does it mean: "the same"...

But I disagree quite strongly with the idea of "/World parameter as 
purely hypothetical, a trick used to gain an intuition/". I mentioned 
the language Clean (no reaction, seems that Haskellians continue to 
ignore it...)

In Clean this IS the IO model. You have such entities as FileSystem, 
which has the Unique Access property, etc. You can put all that in an 
equivalent of the IO Monad, constructed within Clean itself, not as a 


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