Hi all,
I was wondering whether there was any particular reason why OCaml
doesn't allow the user to create open extensible datatypes like exn.
I know that something similar can be created using local exceptions:
module T = struct
type t = exn
type 'a tvariant = (('a -> t), (t -> 'a option))
let createVariant (type s) () =
let module M = struct exception E of s end in
(fun x -> M.E x), (function M.E x -> Some x | _ -> None)
let mkTVariant ((cnstr, _) : 'a tvariant) (x: 'a) = cnstr x
let matchTVariant ((_, destr) : 'a tvariant) (xt: t) = destr xt
end
but it isn't very neat, and it seems that it would not be that difficult to
allow the user to declare types with the same properties as exn.
Thanks,
Leo
--
Caml-list mailing list. Subscription management and archives:
https://sympa-roc.inria.fr/wws/info/caml-list
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
Bug reports: http://caml.inria.fr/bin/caml-bugs
