[Caml-list] What does underscore mean in this type expression?

2008-08-30 Thread Richard Jones 
I'm seeing this type error.  Notice the difference is a lowly
underscore character.

  The implementation libvirt.ml does not match the interface libvirt.cmi:
  Values do not match:
val get_domains :
  (_[ `R ] as 'a) Connect.t -
  ?want_info:bool -
  Domain.list_flag list - 'a Domain.t list * Domain.info list
  is not included in
val get_domains :
  ([ `R ] as 'a) Connect.t -
  ?want_info:bool -
  Domain.list_flag list - 'a Domain.t list * Domain.info list

This syntax doesn't appear to be documented in the manual (unless it's
related to '_a).  What does it mean?

I can supply some reproducer code if needed, but the code is rather
long at the moment.

Rich.

-- 
Richard Jones
Red Hat

___
Caml-list mailing list. Subscription management:
http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
Archives: http://caml.inria.fr
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
Bug reports: http://caml.inria.fr/bin/caml-bugs

Re: [Caml-list] What does underscore mean in this type expression?

2008-08-30 Thread Richard Jones 
On Sat, Aug 30, 2008 at 01:38:31PM +0200, Christophe TROESTLER wrote:
 On Sat, 30 Aug 2008 12:27:18 +0100, Richard Jones wrote:
  
  val get_domains :
(_[ `R ] as 'a) Connect.t -
is not included in
  val get_domains :
([ `R ] as 'a) Connect.t -
  
  This syntax doesn't appear to be documented in the manual (unless it's
  related to '_a).  What does it mean?
 
 It is a weak type as you guessed.  To convince you of that, here is
 some code:
 
 # let x = ref `X;;
 val x : _[ `X ] ref = {contents = `X}

OK ... so how to get rid of the error?  Even supplying a full type for
get_domains in the implementation doesn't get rid of it.

Here's the code if anyone wishes to try:

  http://www.annexia.org/tmp/libvirt.mli
  http://www.annexia.org/tmp/libvirt.ml

  $ ocamlc -c libvirt.mli
  $ ocamlc -c libvirt.ml
  The implementation libvirt.ml does not match the interface libvirt.cmi:
  Values do not match:
  [etc]

Rich.

-- 
Richard Jones
Red Hat

___
Caml-list mailing list. Subscription management:
http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
Archives: http://caml.inria.fr
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
Bug reports: http://caml.inria.fr/bin/caml-bugs