Remi Vanicat a écrit :
> 
> "sebastien FURIC" <sebastien.furic@tni-valiosys.com> writes:
> 
> >  Hi,
> >
> >  What do you think of the following code?
> >
> > # type toto = Toto of int | Titi of string;;
> > type toto = Toto of int | Titi of string
> > # let test t t' = match t, t' with
> >   | ((Toto _ | Titi _), Toto x | Toto x, (Toto _ | Titi _)) when x = 0
> > -> "OK"
> >   | _ -> "KO";;
> > Characters 73-79:
> > Warning: this pattern is unused.
> >   | ((Toto _ | Titi _), Toto x | Toto x, (Toto _ | Titi _)) when x = 0
> > -> "OK"
> >                                           ^^^^^^
> 
> I can't answer to your question, but with your example, one can do a:
> 
> # let test t t' = match t, t' with
>   | ((Toto _ | Titi _), Toto 0
>   | Toto 0, (Toto _ | Titi _)) when x = 0 -> "OK"
>   | _ -> "KO";;
> 
> of course, this is not generalizable to any test.

 I could have even write:

# let test t t' = match t, t' with
  | _, Toto 0 | Toto 0, _ -> "OK"
  | _ -> "KO";;

 The point is that my example is extracted from a "serious" project
where I wrote something like:

| ((Toto _ | Titi _), Toto x | Toto x, (Toto _ | Titi _)) when f(x) = 0
-> ...

 and where type toto has more than 2 constructors.

 Cheers,

 Sébastien.

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