Proposal: Value strict versions of containers

Sebastian Fischer fischer at
Mon May 23 13:31:23 CEST 2011

On Mon, May 23, 2011 at 11:47 AM, Simon Marlow <marlowsd at> wrote:

> I personally would rather have one IntMap with strict and lazy APIs.

I am also in favour of the "same type approach" because it seems it can help
to avoid duplicating the implementations. Would it be efficient to define a
type Data.IntMap.Strict.IntMap with strict fields (also for values) and then
define Data.IntMap.Lazy in terms of this implementation and a wrapper type?

data Lazy a = Lazy { getLazy :: a }

newtype IntMap a = LazyIntMap { getLazyIntMap :: Data.IntMap.Strict (Lazy a)

lookup :: Int -> IntMap a -> Maybe a
lookup n = fmap getLazy . Data.IntMap.Strict.lookup n . getLazyIntMap


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