The semicolon separates a series of expressions. The value of a series of
expressions separated by semicolons is the value of the last expression.
Every expression except the last must evaluate to unit.

The following code snippet

 let w = area#misc#realize ()
 ;

   area#misc#window;;

is the same as

 let w = area#misc#realize ( () ; area#misc#window );;

which is the same as

 let w = area#misc#realize area#misc#window;;

-----Original Message-----
From: owner-caml-list@pauillac.inria.fr
[mailto:owner-caml-list@pauillac.inria.fr]On Behalf Of
briand@aracnet.com
Sent: Wednesday, August 25, 2004 10:23 PM
To: caml-list@pauillac.inria.fr
Subject: [Caml-list] baffled by semicolon



This might really by a lablgtk2 question, but I thought it's probably
more of a ocaml syntax question :

The following works :


let window = GWindow.window ~width:400 ~height:400()
;;

let area = GMisc.drawing_area ~packing:window#add ()
;;

let w = area#misc#realize ()
;

  area#misc#window;;

let drawing = new GDraw.drawable w
;;

However making the simple change

let w = area#misc#realize ()
;;

^^ notice the double semicolon gives an error:
This expression has type unit but is here used with type
  [> `drawable ] Gobject.obj

For the simple reason that w has somehow, mysteriously, become = ()
instead of Gdk.window which is the value it would acquire if it was
only a single semi-colon.

I went back through the manual and really couldn't find anything which
explained the difference between ; and ;; - so it's not at all obvious
to me what's going on here.  I would think that w would take on the value of
evaluating

 area#misc#realize ()

in either case.

???

Brian

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