Re: [Ocaml-lib-devel] Next Step

[Brian H. <bh...@sp...>]

On Mon, 6 Oct 2003, Nicolas Cannasse wrote:

> > 2) The next function returns 'a and throws an execption to indicate the
> > end of elements in one place, and returns 'a option and returns None to
> > indicate the end of elements in another.
> 
> Your eternal battle here :)
> Not yet convinced that exceptions are better - faster - for internal usage,
> but dangerous for the programmer if raised from the API ?
> BTW, there is no Enum.next in the API : it's called Enum.get

Until I can come up with something better, I'm not going to restart the 
debate.

> Your answer here :
> 
> class virtual ['a] enum = object
>     method virtual map : 'b . ('a -> 'b) -> 'b enum
> end

I tried that.  No dice:

$ ocaml
        Objective Caml version 3.07
 
# class virtual ['a] enum = object
      method virtual map : 'b . ('a -> 'b) -> 'b enum
                           --------------------------
  end;;

This type scheme cannot quantify 'b : it escapes this scope.
#

> 
> BTW, objects are certainly the worst part of OCaml. They are tricky,
> difficult to use, and have bad performances (compared to modules instances).
> If you look at Java programmers (or most of the OO programmers actually)
> they're using OO only for prototyping ( interfaces in Java or pure virtual
> classes in C++ ). In Ocaml , you can already prototype by using a module and
> add specialisation with some polymorphic closures. Believe me : you don't
> need objects.

While I'll agree that Java programmers use objects for a lot of things
that Ocaml has better ways of doing, I think objects are the *natural*
representation for enumerations.  You have internal state shared among
multiple functions (data hiding), multiple implementations of the same
methods (inheritance), and a specified contract for the API (interfaces).  
This is OO all over.

Brian