GHC.Event.Unique vs Data.Unique

Michael Schröder mc.schroeder at
Sat Aug 2 06:40:15 UTC 2014

Is there a reason GHC.Event.Unique exists, since we also have Data.Unique?
Or is this just a historical artifact? It looks like they used to have the
same implementation, but have now diverged, with Data.Unique being the more
recent one.

GHC.Event.Unique still uses STM internally, and is as far as I can see the
only part of the base library to do so. Which wouldn't really matter,
except that now basic IO stuff like threadDelay and even putStr (sometimes,
especially in ghci) cannot be used inside unsafeIOToSTM. Which is somewhat
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