On Thu, 13 Dec 2001, Diego Olivier Fernandez Pons wrote:

> I am afraid I do not understand how are cyclic types and OOP related.
> Could you explain more precisely this point ?

Cyclic (aka recursive) types are necessary to type such an expression:
# fun x -> x # run (); x;;
- : (< run : unit -> 'b; .. > as 'a) -> 'a = <fun>

Note that recursive constructed (variant,record) types are not considered
cyclic:  type 'a tree = Leaf | Node of 'a * 'a. Except for objects,
recursive types are often unecessary; allowing them may hide or deplace
type errors, and make error messages difficult to understand. Moreover,
they sensibly complexify the implementation. I don't want to speak for the
OCaml team, but it seems reasonnable to consider that recursive types are
supported in OCaml only because of OOP ...



Alain

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