Re: [Ocaml-lib-devel] Request polymorphic set and map

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

> > People keep saying that they can cut and paste the
> > Functor based Set and Map to get a polymorphic version
> > using the builtin-compare, so that:
> >
> > let s = ExtSet.empty in
> > let s = Ext.set add_element s 0
> >
> > for example, works (the type is deduced like for a list
> > or Hashtble, rather than being manually instantiated.)
> >
> > Is there a plan to put these into Extlib?
> > Another option would be
> >
> > let s = ExtSet.make cmp in ..
> >
> > where cmp is suitable comparator.
>
> What about:
>
> let s1 = ExtSet.make cmp1 in
> let s2 = ExtSet.make cmp2 in
> ...
> let s = ExtSet.union s1 s2

Should raise something like "exception Comparator_differs" if not physical
equality between s1.cmp and s2.cmp.
in functor approach, you cannot actually do it since the comparator is bound
to a type/module so errors are detected at compilation time and not at
runtime. But that's a small tradeoff compared to the ability to define sets
without having to define a module for every type you need.

Nicolas Cannasse