Re: [Caml-list] Warning 28.

[Virgile Prevosto <virgile.prevosto@m4x.org>]

Hello Ivan,

2013/6/5 Ivan Gotovchits <ivg@ieee.org>:
>     | Ref n -> ...
>     ...
>
> where Ref is:
>
> type t =
>   ...
>   | Ref of int
>
> Compiler issues me a warning:
>
> «Warning 28: wildcard pattern given as argument to a constant constructor»
>
> Sorry, but if I understand this wording correctly, then I do not see
> anything criminal in issuing a wildcard pattern to a constant
> constructor. What is wrong?

OCaml is not complaining about your Ref constructor, but another one
that does not have any argument, but is nevertheless given a wildcard
pattern in the matching, as e.g. None in
the following code:

# let f default = function
  | Some n -> n
  | None _ -> default;;
Warning 28: wildcard pattern given as argument to a constant constructor

The 'None _'  is suspicious at best. Tolerating such kind of pattern
reportedly eases generation of OCaml code, and that's why it is a
warning and not a plain error.

Best regards,
--
E tutto per oggi, a la prossima volta
Virgile