Date: Mon, 02 Nov 1998 10:32:08 +0100
From: Christophe Raffalli <Christophe.Raffalli@univ-savoie.fr>
Subject: Sharing inheritance ?
I have a problem with the following situation:
--- class a (x : int) = object val mutable v = x method get = v method set x = v <- x end ;; class b x = object (self) inherit a x as super method getb = self#get method setb = self#set method oldget = super#get end ;; class c x = object (self) inherit a x method getc = self#get method setc = self#set end ;; class d x = object inherit b x inherit c x end ;; (* produces: Warning: the following methods are overriden by the inherited class: get set Warning: this definition of an instance variable v hides a previously defined instance variable of the same name *)
let o = new d 2;; o#setb 3;; o#getc;; (* produces 3 *) o#oldget;; (* produces 2 *)
I understand what is happening, but I would prefer is the default semantic was two merge two values with the same name in an object (giving a type error if their types can not unify).
Then one could have a syntactic sugar to change the name of some value:
class d x = object inherit b x inherit c x with v -> v' end ;; To ask to rename the value v from b as v'. Together with the possibility to bind a name to acces old method, this will allow a total flexibility (I can always do what I want) which is not the case now.
Moreover, the follwing would become possible:
class d = object inherit b 0 with v -> v0 as b0 inherit b 1 with v -> v1 as b1 inherit b 2 with v -> v2 as b2 end ;;
Christophe Raffalli Universite de Savoie
PS: do not forget to add "inherit" and "open ... in" for structure in the next release, that will make some program simpler.
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