Re: Adding manual worker/wrapper transforms to Data.Map

20 Aug 2010


      On Thu, Aug 19, 2010 at 11:46 PM, wren ng thornton <
wren@community.haskell.org> wrote:
...
Johan Tibell wrote:
...
insertWithKey' :: Ord k => (k -> a -> a -> a) -> k -> a -> Map k a ->
Map k a
   insertWithKey' f kx x t0 = kx `seq` go t0
     where
       go t = case t of
         Tip -> singleton kx $! x
         Bin sy ky y l r
             -> case compare kx ky of
                  LT -> balance ky y (go l) r
                  GT -> balance ky y l (go r)
                  EQ -> let x' = f kx x y in seq x' (Bin sy kx x' l r)
As a style issue, I'd suggest using a pattern instead of the first case:
go Tip = singleton kx $! x
   go (Bin sy ky y l r) =
case compare kx ky of
       LT -> balance ky y (go l) r
       GT -> balance ky y l (go r)
       EQ -> let x' = f kx x y in seq x' (Bin sy kx x' l r)
I'll definitely do that in the final version.

-- Johan