[Haskell-cafe] Other transactional arrays?

[Felipe Lessa]

On Fri, Jul 9, 2010 at 7:16 AM, Emil Melnicov <emilmeln at gmail.com> wrote:
>> writeTVector :: TVector a -> Int -> a -> STM ()
>> writeTVector (TVector t#) (I# i#) x = stm $ \s1# ->
>>     case readTVar# t# s1#                    of { (# s2#, (MutableArray a#) #) ->
>>     case writeArray# a# i# x s2#             of { s3# ->
>>     case writeTVar# t# (MutableArray a#) s3# of { s4# ->
>>     (# s4#, () #) }}}
>
> It seems like it works, but I'm in doubt about it's correctness.
> Unfortunately, I don't know much about STM mechanics, so I'm asking
> Cafe users (you :-) for help.

I guess the only problem lies with writeTVector.  I don't know much
about STM implementation details as well, but reading the code for
writeTVector I can't see how it could be rollbacked.  I.e., should
something with writeTVector fail and rollback, how will the old value
get into the mutable array?

Cheers :)

-- 
Felipe.