Lennart Augustsson wrote:
I don't see any breaking of referential transparence in your code.
Every time you do an IO operation the result is basically
non-deterministic since you are talking to the outside world.
You're assuming the IO has some kind of semantics that Haskell makes
no promises about.
I'm not saying that this isn't a problem, because it is.
But it doesn't break referential transparency, it just makes the
semantics of IO even more complicated.
+1
If we are in a situation where really have to take this seriously, we
already have a well-known standard trick for this kind of problem:
refine the monad! We can always define NonInterlavedIO monad for the
operations that does not use unsafeInterleaveIO. We have been doing this
all the time including the recent STM stuff.
(I don't have a formal proof that unsafeInterleaveIO cannot break RT,
but I've not seen an example where it does yet.)
-- Lennart
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