[Haskell-cafe] Control.Concurrent.STM.old?

Tim Harris (RESEARCH) tharris at microsoft.com
Mon Jan 21 21:07:07 EST 2008


I don't think we included this in the version we checked in.

It should be fairly easy to add to the current implementation: it will mirror ReadTVar except that the old value is always selected.

I'm afraid I can't remember exactly why we didn't include it.  One reason might have been that it would constrain alternative implementations -- for example one built over hardware transactional memory which might not necessarily provide access to the old state.


-----Original Message-----
From: haskell-cafe-bounces at haskell.org [mailto:haskell-cafe-bounces at haskell.org] On Behalf Of Thomas DuBuisson
Sent: 19 January 2008 00:14
To: haskell-cafe at haskell.org
Subject: [Haskell-cafe] Control.Concurrent.STM.old?

Does the 'old' function referenced in the SPJ and Tim Harris data
invariants paper stil exist?  It is of type STM a -> STM a and allowed
invariants to compare old TVar values with new ones.  I can't find it in
any of the Haddocks or the code (and the 'check' funciton is not
commented in the Haddock).


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