On 30/12/2011 01:40, Scott Turner wrote:
On 2011-12-29 19:44, Steve Horne wrote:
[Interaction with its environment] is as much an aspect of what
Haskell defines as the functional core.
Switching mental models doesn't change the logic
But it does. Other languages do not support the distinction between pure
functions and I/O effects.
Agreed. I said basically the same thing right at the start. This doesn't
change any logic, though.
Either way, at run-time, Haskell is impure.
No big deal. Who would want to use a language that you would call
"pure"? Haskell has referential transparency. In Haskell, you have
assurance that any function without IO in its type is as pure as the
lambda calculus.
Absolutely. In my original post, of course, I made my "big implicit
IORef parameter" argument that says C too is referentially transparent,
but I also pointed out another view of transparency - the politician who
buries the relevant in a huge pile of the irrelevant is not being
transparent - and pointed out that in Haskell you can have zero, one or
many IORefs - you can focus in on what is relevant.
I actually thought this point would make Haskell advocates happy, but no
sign of that yet.
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