Add variants of split

[nomeata]

I regularly find myself in the need of splitting a map into two maps. For that we currently have these two functions:

split :: Ord k => k -> Map k a -> (Map k a, Map k a)
splitLookup :: Ord k => k -> Map k a -> (Map k a, Maybe a, Map k a) 

Usually, split is useless to me because information (the element right on the border) gets lost. splitLookup preserves the information, but often I want the element at the border to simply be in one of the two output maps. So I would like to see

splitL :: Ord k => k -> Map k a -> (Map k a, Map k a)
splitR :: Ord k => k -> Map k a -> (Map k a, Map k a)

with these properties

uncurry union (splitL k m) == m
uncurry union (splitR k m) == m
all (<= k) (keys (fst (splitL k m))
all (> k)  (keys (snd (splitL k m))
all (< k)  (keys (fst (splitR k m))
all (>= k) (keys (snd (splitR k m))

#167 is related.

I will bring this before the libraries list; this issue is mostly for future reference and discoverability.

[nomeata]

I was pointed to splitAntitone, which solves this nicely (via splitL k = splitAntitone (<= k) and splitR k = splitAntitone (< k)) . Closing for now, unless people speak up who really want these convenience functions.

[Icelandjack]

spanAntitone, not split.

[nomeata]

Of course.

[nomeata]

spanAntitone will do fine, closing this.