Adding manual worker/wrapper transforms to Data.Map

[wren ng thornton]

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)

-- 
Live well,
~wren