> > Why can't you do this kind of in ocaml?  Returning something like a
> > "next" function would seem to give you a very basic (but usable)
> > iterator.  Which part of the iterator abstraction can't you do?
>
> I suggest you try it. I don't know how to answer the question.
> I think the answer is 'C++ templates provide functorial
> polymorphism (polyadicity), Ocaml has no such expressive power.'
>
> HOF's like 'map' and 'fold' make sense
> for polynomial data structures -- lists and trees etc.
> But you have to write 'List.map' or 'Array.map'. There
> is no single 'map' which works for all data structures
> in Ocaml.

There is ExtLib Enum.map that's pretty good at doing that.

> There is in C++, and its a one line idiom:
>
> // STL copy
> for(; i!=e; ++i) *o++ = *i++;
>
> Fold is as easy to define (called Accumulate in STL).
>
> These definitions are polyadic. They work for ALL
> data structures -- provided they have iterators
> of course :D

That's exactly the same as ExtLib enums : define an enumerator for your data
structure, and you can apply a full range of algorithms on it. I don't
really understand the difference with  STL.

Regards,
Nicolas Cannasse

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