From: Gerd Stolpmann <Gerd.Stolpmann@darmstadt.netsurf.de>
To: caml-list@inria.fr
Subject: The option -rectypes
Date: Wed, 24 Nov 1999 01:59:36 +0100
Message-Id: <99112402223302.32002@ice>
I have some code that compiled in 2.02, but in 2.03 I need the new option
-rectypes of the compilers.
My class definitions look like (the signatures)
class type [ 'node ] extension =
object ('self)
method clone : 'self
method node : 'node
method set_node : 'node -> unit
end
;;
class type [ 'ext ] node =
object ('self)
constraint 'ext = 'ext node #extension
method extension : 'ext
(* ... more methods ... *)
end
;;
This works in both versions out of the box. If I add
val f : 'a node extension as 'a
the 2.03 compiler only accepts the type if I add -rectypes. I have several
questions:
- What is the effect of -rectypes? (I did not find a good explanation in the
manual.)
- What is the background of this change?
- I have thought about the type 'a node extension as 'a. If I apply the
constraint of "node", the condition must hold that
('a node extension as 'a) node extension
unifies with
('a node extension as 'a) node #extension
Normally, a closed class type does not unify with an open class type,
and I wonder why this is accepted at all.
Without -rectypes, the 2.03 compiler only accepts
val f : 'a node #extension as 'a
but this is a much more difficult type.
Gerd
-- ---------------------------------------------------------------------------- Gerd Stolpmann Telefon: +49 6151 997705 (privat) Viktoriastr. 100 64293 Darmstadt EMail: Gerd.Stolpmann@darmstadt.netsurf.de (privat) Germany ----------------------------------------------------------------------------
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