Interesting.
Would be used like this:
uniquePermutations xs = runST $ strictToLazyST $ (uniquePermutationsST
xs)
After also swapping `runST` to the lazy version, it compiles and runs. Thank
you!
-----Original Message-----
From: Peter Gammie [mailto:pete...@gmail.com]
Sent: Mittwoch, 22. Juli 2009 01:25
To: Christian Klauser
Cc: glasgow-haskell-users@haskell.org
Subject: Re: "Could not deduce (MArray (STUArray s) Int (ST s)) from context
()" when applying runST
On 22/07/2009, at 9:16 AM, Christian Klauser wrote:
> Thank you, works indeed with the strict ST monad. Didn't think of
> that. But
> makes kind of sense not to define these instances, since unboxed
> values
> cannot have their computation delayed. It's a bit unfortunate,
> however, that
> a single use
> of an unboxed array "forces" the whole state thread to become strict.
Hmm. Have you seen the strictToLazyST function?
http://www.haskell.org/ghc/docs/latest/html/libraries/base/Control-Monad-ST-
Lazy.html#v%3AstrictToLazyST
cheers
peter
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