[Haskell-cafe] Semantics of uniqueness types for IO (Was: Why can't
Haskell be faster?)
apfelmus at quantentunnel.de
Thu Nov 1 10:46:16 EDT 2007
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?
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