From: "Christoph Höger" <christoph.hoeger@tu-berlin.de>
To: caml users <caml-list@inria.fr>
Subject: [Caml-list] polymorphic methods
Date: Fri, 18 Dec 2015 10:18:42 +0100 [thread overview]
Message-ID: <5673CF72.4030808@tu-berlin.de> (raw)
Dear all,
I am attempting to store polymorphic methods in classes (i.e. keep the
type variables out of the class-type by putting them directly into the
method signatures).
However, I have some trouble when it comes to convince the compiler that
my code is typecorrect:
type ('a, 'b) f_arg = < x : 'b; .. > as 'a ;;
let f : 'a 'b . (('a,'b) f_arg) -> 'b = fun a -> a#x ;;
class foo = object method f : 'a 'b . ('a, 'b) f_arg -> 'b = f end ;;
yields:
Error: This expression has type
'a 'b. (< x : 'b; .. > as 'a) -> 'b
but an expression was expected of type
'c 'b. (< x : 'b; .. > as 'c) -> 'b
The type variable 'd occurs inside 'd
What is 'd? Why do these types not unify?
--
Christoph Höger
Technische Universität Berlin
Fakultät IV - Elektrotechnik und Informatik
Übersetzerbau und Programmiersprachen
Sekr. TEL12-2, Ernst-Reuter-Platz 7, 10587 Berlin
Tel.: +49 (30) 314-24890
E-Mail: christoph.hoeger@tu-berlin.de
next reply other threads:[~2015-12-18 9:18 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-18 9:18 Christoph Höger [this message]
2015-12-18 10:07 ` Leo White
-- strict thread matches above, loose matches on Subject: below --
2003-03-12 23:07 Damien
2003-03-13 0:56 ` brogoff
2003-03-13 1:56 ` Jacques Garrigue
2003-03-13 9:04 ` Damien
2003-03-13 9:27 ` Jacques Garrigue
2003-03-13 14:49 ` Damien
2003-03-13 9:41 ` Olivier Andrieu
2002-08-23 15:46 [Caml-list] Polymorphic methods Frederic Tronel
2002-08-23 17:32 ` Fred Smith
2002-08-23 18:21 ` Remi VANICAT
2002-07-14 23:16 [Caml-list] polymorphic methods nadji
2002-07-15 1:05 ` Jacques Garrigue
2002-07-15 2:08 ` Brian Smith
2002-07-15 16:24 ` nadji
2001-11-19 15:29 [Caml-list] Polymorphic methods Alain Frisch
2001-11-20 0:29 ` Jacques Garrigue
2001-11-20 9:33 ` Alain Frisch
2001-11-20 20:55 ` Xavier Leroy
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