On 4 Nov 2009, at 13:36, Alberto G. Corona wrote:
Artyom.
I know what uniqueness means. What I meant is that the context in
which uniqueness is used, for imperative sequences:
(y, s')= proc1 s x
(z, s'')= proc2 s' y
.....
is essentially the same sequence as if we rewrite an state monad to
make the state explicit. When the state is the "world" state, then
it is similar to the IO monad.
Yes, as long as there is a single thing that is being updated there's
little difference between the state monad and a unique type. But
uniqueness typing is more general. For instance, a function which
updates two arrays
f (arr1, arr2) = (update arr1 0 'x', update arr2 0 'y')
is easily written in functional style in Clean, whereas in Haskell we
need to sequentialize the two updates:
f (arr1, arr2)
= do writeArray arr1 0 'x'
writeArray arr2 0 'y'
You can find a more detailed comparison in my thesis (https://www.cs.tcd.ie/Edsko.de.Vries/pub/MakingUniquenessTypingLessUnique-screen.pdf
, Section 2.8.7).
-Edsko
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