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RE: [Caml-list] Deep copy
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Date: -- (:)
From: zze-MARCHEGAY Michael stagiaire FTRD/DTL/LAN <michael.marchegay@r...>
Subject: RE: [Caml-list] Deep copy
> De : Eray Ozkural [mailto:erayo@cs.bilkent.edu.tr]
> Envoyé : lundi 15 juillet 2002 17:03
> 
> 
> On Monday 15 July 2002 13:06, zze-MARCHEGAY Michael stagiaire 
> FTRD/DTL/LAN 
> wrote:
> > Hi all,
> >
> > I'm writting a program that manipulates a graph structure 
> and I need to
> > make deep copies of some of the graph nodes. The function 
> Oo.copy donesn't
> > perform a deep copy and I haven't found any other that 
> could make it.
> 
> You mean something like creating a new object on the heap and 
> copying over the 
> contents of an existing object.
> 
> If this were C++ all you had to do would be invoking the copy 
> constructor
>  Node* x = new Node(old_node);
> 
> From the documentation OO.copy does look like a deep copy operation:
> 
> val copy : < .. > -> < .. >
> Oo.copy o returns a copy of object o, that is a fresh object 
> with the same 
> methods and instance variables as o

In fact, if an object 'a' contains an attribute 'b' that is another 
object, Oo.copy on 'a' gives a copy of 'a' in which the attribute
'b' is **physically** equal to the copied attribute from 'a'.

Example:
class a = 
  object 
    val mutable b = new b
    method get_b = b
  end
and b = 
  object
    val mutable c = "1"
    method set_c x =  c <- x
    method print_c = print_string ("c=" ^ c ^ "\n")  
  end

let aa = new a
let aa' = Oo.copy aa

let _ = 
  aa#get_b#set_c "3";
  aa#get_b#print_c;
  aa'#get_b#print_c

gives:
c=3
c=3

whereas a deep copy would give:
c=3
c=1

> 
> Curious,
>  
> -- 
> Eray Ozkural <erayo@cs.bilkent.edu.tr>
> Comp. Sci. Dept., Bilkent University, Ankara
> www: http://www.cs.bilkent.edu.tr/~erayo
> GPG public key fingerprint: 360C 852F 88B0 A745 F31B  EA0F 
> 7C07 AE16 874D 539C
> 
> 
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