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

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

> > What do you think of this:
> >
> > (* default merge = fun x y -> x *)
> > val union : ?merge:('b -> 'b -> 'b) -> ('a, 'b) t -> ('a, 'b) t -> ('a,
> 'b) t
> >
> > (* a merge function must be given to inter *)
> > val inter : merge:('b -> 'c -> 'd) -> ('a, 'b) t -> ('a, 'c) t -> ('a,
'd)
> t
> >
> > val diff : ('a, 'b) t -> ('a, 'c) t -> ('a, 'b) t
>
> Why not generalize a little more ?
>
> val union : merge:('b -> 'c -> 'd) -> ('a,'b) t -> ('a,'c) t -> ('a,'d) t
>
> The only problem is that we can't use "identity" as default merger.
>
> Nicolas

After a second though I think it's little overweighted to make the user
specify a merge function. Why not simply specify that in such cases, the
item of the first map is selected ? That seems more reasonable.

Nicolas