Closed
Description
There are
adjust :: Ord k => ( a -> a) -> k -> Map k a -> Map k a
update :: Ord k => ( a -> Maybe a) -> k -> Map k a -> Map k a
alter :: Ord k => (Maybe a -> Maybe a) -> k -> Map k a -> Map k abut
upsert :: Ord k => (Maybe a -> a) -> k -> Map k a -> Map k avariant is missing.
While it's definable with upsert f = alter (Just . f), I'd like to have it already in the library.
Compare implementation for Map:
even alter is tagged as INLINEABLE, the optimization may or may not happen.
alter :: Ord k => (Maybe a -> Maybe a) -> k -> Map k a -> Map k a
alter = go
where
go :: Ord k => (Maybe a -> Maybe a) -> k -> Map k a -> Map k a
go f !k Tip = case f Nothing of
Nothing -> Tip
Just x -> singleton k x
go f k (Bin sx kx x l r) = case compare k kx of
LT -> balance kx x (go f k l) r
GT -> balance kx x l (go f k r)
EQ -> case f (Just x) of
Just x' -> Bin sx kx x' l r
Nothing -> glue l rvs
upsert :: Ord k => (Maybe a -> a) -> k -> Map k a -> Map k a
upsert = go
where
go :: Ord k => (Maybe a -> a) -> k -> Map k a -> Map k a
go f !k Tip = singleton k (f Nothing)
go f k (Bin sx kx x l r) = case compare k kx of
LT -> balance kx x (go f k l) r
GT -> balance kx x l (go f k r)
EQ -> Bin sx kx (f (Just x)) l rIn fact, I'd like having upsertF variant as well.
It would be less code/branches then with alterF.