[Haskell-cafe] Implementing ParseChart with Data.Map
ndmitchell at gmail.com
Mon Jun 2 18:41:30 EDT 2008
> case insertLookupWithKey (\_ -> Set.union) k (Set.singleton v) chart of
> (Nothing, chart) -> Just chart
> (Just set, chart) | Set.member v set -> Nothing
> | otherwise -> Just chart
> but notice that the set is still traversed twice.
Yes, I missed that bit. I don't see any way of reducing that, other
than using an unsafePerformIO and IORef to track the combining
function - which is probably a really bad idea.
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