Re: [Ocaml-lib-devel] Map with set operations over the keys

[Nicolas C. <war...@fr...>]

> If you want to provide a generic point-wise binary combinator for maps,
> the type should be something like:
>
> (key -> 'a option -> 'b option -> 'c option) ->
>    'a t -> 'b t -> 'c t
>
> The first argument is never called with two None arguments, and
> you might prefer to use exception to signal elements to remove, instead
> of a None result, so another type could be:
>
> (key -> 'a -> 'c) -> (key -> 'a -> 'b -> 'c) -> (key -> 'b -> 'c) ->
>   'a -> 'b t -> 'c t
>
>
> In my experience, having such a generic point-wise combinator on
> map-like structures is really useful. Maybe you also want special cases
> (as a convenience for the user but also to optimize the implementation),
> but I really believe a generic version should be offered in the interface.
>
> -- Alain

I agree too.
One generic function for specific uses plus some specific functions  merge /
union / diff for fast (no boxing, no callback) and easy usage.

Nicolas