Re: [Haskell-cafe] mapping unfreeze over an IntMap of IOUArrays

chad.scherrer:

Hello cafe,

I've hit a bit of a monadic snag here...

I'm scanning a big file, building a table of statistics. I end up with something like

IO (IntMap (IOUArray Int Double))

Once I've read in the whole file and built my statistics, I don't need any more updates, so I'd like to do something like

IntMap (IOUArray Int Double) -> IO (IntMap (UArray Int Double)),

using unsafeFreeze. I'm getting stuck here, since the IntMap library is not so monad-friendly.

Hmm. So you'd need to construct a new IntMap, made by fmap'ping unsafeFreeze over each element of the old map. -- Don