> Haskell position (as I understand it)
> -------------------------------------
> Haskell is incapable of desribing IO, it can only evaluate an expression
> of type IO (). This expression is used by an 'IO monad machine' (which
> is not part of Haskell) to actually execute IO operations. Because the
> IO monad machine is not part of Haskell, it can freely make use of all
> the horrors one would expect in a typical imperative language without
> damaging pure functionality in Haskell itself.
In Haskell you ONLY define a VALUE of an abstract type IO that DESCRIBES
the changes the World would suffer WHEN that value is operationally
interpreted. So, saying that Haskell is incapable of describing I/O is,
at least, a misunderstanding.
That abstract type can be viewed as a state monad whose state is the
World, i.e.
IO a = (World -> (a, World))
and so you can also describe functions going from one state of the world
to another (producing a value as result), but only in abstract ways.
The 'monad machine', as you call it, is the one responsible for the
operational execution of IO values.
I don't know how does Clean work with I/O, and I can not conlude
anything from your explanation, nor I can see how they colud manage to
avoid the 'horrors' of imperative languages you attach to Haskell. I
would appreciate more insight in this subject.
Fidel.
