Version française
Home     About     Download     Resources     Contact us    
Browse thread
multiple inheritance, bug or feature ?
[ Home ] [ Index: by date | by threads ]
[ Search: ]

[ Message by date: previous | next ] [ Message in thread: previous | next ] [ Thread: previous | next ]
Date: -- (:)
From: Oliver Bandel <oliver@f...>
Subject: Re: [Caml-list] multiple inheritance, bug or feature ?
On Sat, Feb 25, 2006 at 12:01:00PM +0100, sejourne_kevin wrote:
> Hello :
> 
> 
> Consider the following sample :
> 
> class a =
> object
>   val mutable x = 0
>   method set v = Printf.printf "%d\n" x;x <- v
> end
> ;;
[...]
 
> class c :
>   object
>     val mutable x : int
>     val mutable y : int
>     method set : int -> unit
>     method set_x_a : int -> unit
>     method set_x_a' : int -> unit
>     method set_y : int -> unit
>   end
> 
> let d = new c;;
> val d : c = <obj>
> 
> d#set_x_a 3;;
> 0
> - : unit = ()
> 
> d#set_x_a' 2;;
> 0
> - : unit = ()
> 
> 
> When I wrote this program I expect this behavior but
> according to the warnings M the result should be 3.

Why do you think the expected behaviour should be
printing the 3?

Your method prints the old value, not the new value.

=======================
# let o = new c;;
val o : c = <obj>
# o#set_x_a 10;;
0
- : unit = ()
# o#set_x_a 20;;
10
- : unit = ()
# o#set_x_a 30;;
20
- : unit = ()
# 
=======================


If you want to print the current value after update,
you should also write your code in the way it it does this.
So, you should write it in this way:

  method set v = x <- v; Printf.printf "%d\n" x


Ciao,
   Oliver