Re: [Caml-list] ocaml 4.03 and warning 52 : argument of this constructor should not be matched against a constant pattern

[Gabriel Scherer <gabriel.scherer@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1544 bytes --]

We now have a section of the reference manual (which has been updated to
4.03) on Warnings, and this particular warning is documented there:
  http://caml.inria.fr/pub/docs/manual-ocaml/comp.html#s:comp-warnings

Feedback (for example as Mantis tickets) on which warnings are confusing
and would deserve additional documentation -- or even patches to provide
this documentation -- are warmly welcome.

On Wed, Apr 27, 2016 at 5:22 AM, William <r.3@libertysurf.fr> wrote:

> Hello,
>
> with ocaml 4.03, I came with many warnings such as this one :
>
> let lst = [] in
> try
>    let fst = List.hd lst in
>    Printf.printf "fst:%s\n" fst
> with
> | Failure "hd" -> Printf.printf "empty list\n";;
>
> Characters 123-127:
> | Failure "hd" -> Printf.printf "empty list\n";;
>            ^^^^
> Warning 52: the argument of this constructor should not be matched against
> a
> constant pattern; the actual value of the argument could change
> in the future.
>
>
>
> It occurs typically for Failure "hd", Failure "tl", Failure
> "float_of_string", Failure "int_of_string", Failure "lexing: empty token",
> Invalid_argument "Filename.chop_extension", ...
>
> How are we supposed to handle this nicely with the standard library ? Is
> there a better approach to catch those exceptions ?
>
>
> Best regards,
>
> William
>
> --
> Caml-list mailing list.  Subscription management and archives:
> https://sympa.inria.fr/sympa/arc/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs
>

[-- Attachment #2: Type: text/html, Size: 2502 bytes --]