[Haskell] TArray?

Jan-Willem Maessen jmaessen at alum.mit.edu
Tue Dec 13 09:52:27 EST 2005

On Dec 13, 2005, at 8:46 AM, Simon Marlow wrote:
> [In response to another plea for TArrays]

> 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).

Actually, in that case it might be more useful to have a TMVar  
containing an array.  But I suspect the need for this use case is  
small.  I know a ton of uses for transactionally-updated arrays for  
which the goal is to permit concurrent access to independent array  
elements (concurrent hash tables come to mind as an obvious use case  
where transactions make life vastly simpler).

You might ask Tim Harris whether there's a reasonably simple, clever  
way to do this
using arrays + CAS.  I believe such a trick exists---you might end up  
waking too many threads on a write, but you'd get read/write  
concurrency at least.


> Cheers,
> 	Simon
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