[Haskell-cafe] Semantics of uniqueness types for IO (Was: Why
can't Haskell be faster?)
arnarbi at gmail.com
Thu Nov 1 10:59:43 EDT 2007
I'm new here, so sorry if I'm stating the obvious.
On Nov 1, 2007 2:46 PM, apfelmus <apfelmus at quantentunnel.de> wrote:
> Stefan Holdermans wrote:
> > Exposing uniqueness types is, in that sense, just an alternative
> > to monadic encapsulation of side effects.
> While *World -> (a, *World) seems to work in practice, I wonder what
> its (denotational) semantics are. I mean, the two programs
> loop, loop' :: *World -> ((),*World)
> loop w = loop w
> loop' w = let (_,w') = print "x" w in loop' w'
> both have denotation _|_ but are clearly different in terms of side
> effects. (The example is from SPJs awkward-squad tutorial.) Any pointers?
For side-effecting program one has to consider bisimilarity. It's
common that semantically equivalent (under operational or denotational
semantics) behave differently with regard to side-effects (i/o) - i.e.
they are not bisimilar.
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