On Oct 28, 2005, at 06:08, Aleksey Nogin wrote:

> AFAIU, there are two warnings - "Y" for variables bound with let  
> and "Z" for variables bound by pattern matching. By default, Y is  
> enabled and Z is not.

The rules for Y are a bit complex.  They are designed to match our style
of programming, where we sometimes document patterns by giving names to
all the arguments, even if they are unused.

Y will warn you on all variables bound with an "as" (in a let-in or a
match).  For the other variables of a let-in pattern, it will warn you
only if all of them are unused.  Examples:

   let (x, y) = (0, 0) in 0;;            (* warning on x and y *)
   let (x, y) = (0, 0) in x;;            (* no warning *)

   let (x, y) as z = (0, 0) in (x, y);;  (* warning on z *)
   match 1 with _ as z -> 1;;            (* warning on z *)

Variables whose names start with _ are always ignored for the  
purposes of
these warnings (both Y and Z):

   let (_x, y) = (0, 0) in 0;;           (* warning on y *)
   let (_x, y) = (0, 0) in _x;;          (* warning on y *)

Z will warn you on all unused variables bound by "let-in" or "match",
except the ones that are (or would be) reported by Y.  Note that it  
doesn't
make much sense to have Y disabled and Z enabled.

Pattern-matchings introduced by the "fun" and "function" keywords behave
like the ones that start with "match".


> Use "ocamlc -wA" to enable all the warnings.

That should be "ocamlc -w A" with a space.

-- Damien