Version française
Home     About     Download     Resources     Contact us    

This site is updated infrequently. For up-to-date information, please visit the new OCaml website at

Browse thread
[Caml-list] copy of parametrized object
[ Home ] [ Index: by date | by threads ]
[ Search: ]

[ Message by date: previous | next ] [ Message in thread: previous | next ] [ Thread: previous | next ]
Date: 2003-06-24 (11:15)
From: Bow-Yaw Wang <bywang@s...>
Subject: [Caml-list] copy of parametrized object


I'd like to know how to make independent copies of parameterized 
objects. Consider the following example:

# class ['a] t = object method id (x:'a) = x end;;
class ['a] t : object method id : 'a -> 'a end
# let o = new t;;
val o : '_a t = <obj>
# let p = Oo.copy o;;
val p : < id : '_a -> '_a > = <obj>
# o#id 1;;
- : int = 1

After defining a simple parameterized class t, I create an
object o of type '_a t and make p as a copy. After the type 
'_a is instantiated to int, I'd expect p to retain its type
< id : '_a -> '_a >. However, 

# p;;
- : < id : int -> int > = <obj>

So my questions are:

1. Is there a way to make a copy of o so that it can be 
instantiated differently?
2. If not, is there any type-theoretic explanation? I'm
just curious if it may make type system unsound.

I'm aware of polymorphic methods. Unfortunately, the
project I'm working on uses parameterized classes. Using
polymorphic methods doesn't seem to be feasible at the
moment. :(

Thanks in advance,


To unsubscribe, mail Archives:
Bug reports: FAQ:
Beginner's list: