On Sun, Jul 25, 2004 at 04:17:55PM +0800, Martin Jambon wrote:
> 
> I need a functional data structure that has a decent efficiency (i.e.
> not lists) and can represent `sets of named containers' so that I can
> find a container in a set, remove it from the set, update it and put it
> back into the set.
> 
> val find : elt -> t -> elt  (* yes! *)
> 
> Finally I just copy-pasted set.mli and set.ml and inserted a find
> function... but is there a better solution?

What I did when faced with a similar problem was:

  module MySet =
    struct
      module BaseSet = Set.Make(
        struct
          ....
        end)
      include BaseSet
      let find elt set = ...
    end

Now of course that will only handle one data type. If you want
polymorphism, I suppose you could try something like:

  module MySet =
    struct
      module Make =
        functor(SomeMod:SOMETYPE) ->
          struct
            include Set.Make
            let find elt set = ...
          end
    ....
    end

Though I haven't tried the more general approach.

-- 
Matt Gushee                 When a nation follows the Way,
Englewood, Colorado, USA    Horses bear manure through
mgushee@havenrock.com           its fields;
http://www.havenrock.com/   When a nation ignores the Way,
                            Horses bear soldiers through
                                its streets.
                                
                            --Lao Tzu (Peter Merel, trans.)

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