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|
let default_duplicate _ _ = invalid_arg "duplicate key"
let default_missing _ _ = None
let zip_by (type k) ?(duplicate = default_duplicate)
?(missing = default_missing) (compare : k -> _) key_of xs ys =
let (module M) = Map_ext.make compare in
let to_map xs =
xs
|> List.fold_left
(fun m x ->
m
|> M.update (key_of x) @@ function
| None -> Some x
| Some y -> duplicate x y)
M.empty
in
M.merge
(fun _ x y ->
match (x, y) with
| Some x, Some y -> Some (x, y)
| Some x, None -> missing `R x
| None, Some y -> missing `L y
| None, None -> None)
(to_map xs) (to_map ys)
|> M.bindings |> List.map snd
|
