On 12/13/05, Simon Marlow <[EMAIL PROTECTED]> wrote: > On 13 December 2005 13:11, Sebastian Sylvan wrote: > > > On 12/13/05, Tomasz Zielonka <[EMAIL PROTECTED]> wrote: > >> On Tue, Dec 13, 2005 at 01:32:46PM +0100, Sebastian Sylvan wrote: > >>> Are there plans to include a mutable array for use in the STM monad, > >>> or a good reason for why this is not needed? Also, an unboxed > >>> version would be nice. > >> > >> Why not use an (Array idx (TVar a)) ? > > > > Ah.. Good thinking! > > This should work for in the STM monad for anything you would IOArray > > for in the IO monad, if you write proper instances for MArray of > > course... > > > > It's a bit inefficient, an extra indirection (compared to a primitive > > implementation) but that shouldn't matter too much for the general > > case. And the TVars themselves introduces some extra overhead, I would > > suppose (which could be per-array rather than per-element, without > > losing the property that only writes to the same element causes > > retries). > > It gets even trickier if you want an unboxed mutable array in the STM > > monad. > > > > But still, it's useful and I think a mutable array for the STM monad > > should be in the libraries. It could be implemented as an Array at > > first, and perhaps later switch to a more efficient representation. > > In the past I have used arrays of TVars, as Thomasz suggested. It would > indeed be better to have a primitive STM array, the only problem with > this is the extra complexity. One simplifying assumption is that it > should consider changes at the level of the whole array, rather than > per-element (otherwise you'd use an array of TVars).
There is no plan to provide an implementation of this (the Array-of-TVar approach) in the libs? With an MArray instance? It would be nice if you could just plug i into existing functions operating on MArray... /S -- Sebastian Sylvan +46(0)736-818655 UIN: 44640862 _______________________________________________ Haskell mailing list Haskell@haskell.org http://www.haskell.org/mailman/listinfo/haskell
