[Haskell-cafe] Re: memoization

[John Lato]

I just discovered that changing DiffArray to a plain Array improves
performance of my code by almost a factor of 10.  Bitten by DiffArray
yet again!

John

-- this is no good, just change DiffArray to Array.
> update :: (Char -> [Int]) -> DiffArray Int ModP -> Char -> DiffArray Int ModP
> update lookup arr c = arr // (map calc . lookup $ c)
>  where
>    calc i = (i, (arr ! i) + (arr ! (i-1)))