Missing functions

[treeowl]

It would be very nice to be able to combine member and lookup:

memberLookup :: Ord k => k -> Map ph k v -> Maybe (Key ph k, v)

Using lookup requires the value to be forced in order to perform the lookup, which can lead to space leaks under some circumstances. It would be good to have one or more of the following:

lookupA :: (Ord k, Applicative f) => Key ph k -> Map ph k v -> f v
lookupSolo :: Ord k => Key ph k -> Map ph k v -> Solo v
lookup# :: Ord k => Key ph k -> Map ph k v -> (# v #)