From: "T. Kurt Bond" <tkb at tkb.mpl.com>
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Message-ID: <16816.53453.797569.169356 at tkb.mpl.com>
Date: Fri, 3 Dec 2004 15:47:09 -0500
To: lablgtk at kaba.or.jp
Subject: GUtil.memo constraint too restricive?


Is there a bug in GUtil.memo?  Should the constraint on that class be 

    constraint 'a = <get_oid: int; ..>

instead of 

    constraint 'a = <get_oid: int>

?

Here's a lablgtk2 toplevel session with lablgtk-2.4.0 and O'Caml
3.08.1:

	    Objective Caml version 3.08.1

    # let e = GEdit.entry ~text:"some text" ();;
    val e : GEdit.entry = <obj>
    # let m = new GUtil.memo ();;
    val m : < get_oid : int > GUtil.memo = <obj>
    # m#add e;;
    Characters 6-7:
      m#add e;;
	    ^
    This expression has type GEdit.entry but is here used with type
      < get_oid : int >
    Only the first object type has a method activates_default

    # class ['a] nemo () = object
      constraint 'a = <get_oid: int; ..>
      val tbl = Hashtbl.create 7
      method add (obj : 'a) = Hashtbl.add tbl obj#get_oid obj
      method find (obj : GObj.widget) = Hashtbl.find tbl obj#get_oid
      method remove (obj : GObj.widget) = Hashtbl.remove tbl obj#get_oid
    end;;

    class ['a] nemo :
      unit ->
      object
	constraint 'a = < get_oid : int; .. >
	val tbl : (int, 'a) Hashtbl.t
	method add : 'a -> unit
	method find : GObj.widget -> 'a
	method remove : GObj.widget -> unit
      end
    # let n = new nemo ();;
    val n : < get_oid : int; _.. > nemo = <obj>
    # n#add e;;
    - : unit = ()
    # n#find e#coerce;;
    - : GEdit.entry = <obj>
    # 

Am I missing something obvious?
-- 
T. Kurt Bond, tkb@tkb.mpl.com