[Haskell-cafe] On the purity of Haskell

[Jerzy Karczmarczuk]

Le 28/12/2011 22:45, Steve Horne a écrit :
> Yes - AT COMPILE TIME by the principle of referential transparency it 
> always returns the same action. However, the whole point of that 
> action is that it might potentially be executed (with potentially 
> side-effecting results) at run-time. Pure at compile-time, impure at 
> run-time. What is only modeled at compile-time is realized at 
> run-time, side-effects included.
> (...)
>
> I hope If convinced you I'm not making one of the standard newbie 
> mistakes. I've done all that elsewhere before, but not today, honest.
Sorry, perhaps this is not a standard newbie mistake, but you - 
apparently - believe that an execution of an action on the "real world" 
is a side effect.

I don't think it is.
Even if a Haskell programme fires an atomic bomb, a very impure one, 
/*there are no side effects within the programme itself*/.
If you disagree, show them.

I don't think that speaking about "compile-time purity" is correct.

Jerzy Karczmarczuk


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