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Message-ID: <6b8a9142050910114072a5e441 at mail.gmail.com>
Date: Sat, 10 Sep 2005 20:40:58 +0200
From: Remi Vanicat <remi.vanicat at gmail.com>
Reply-To: remi.vanicat at gmail.com
To: "romildo at uber.com.br" <romildo at uber.com.br>
Subject: Re: Wrapping a new widget
Cc: lablgtk at math.nagoya-u.ac.jp
In-Reply-To: <20050910174838.GA16269 at malaquias>
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2005/9/10, romildo at uber.com.br <romildo at uber.com.br>:
> Hi.
[...]
> When compiling the test program with compiler
> option -i, we can see the infered types of the
> values:
> 
> $ ocamlc -i lablgtk.cma gtkInit.cmo gExtra.cmo lablgtkextra.cma test-extra.ml -o test-extra
> File "test-extra.ml", line 10, characters 2-50:
> Warning: this expression should have type unit.
> val window : GWindow.window
> val canvas : GObj.widget
> val main : unit -> unit
> 
> I was expecting the type of canvas to be GExtra.plot_canvas
> instead of GObj.widget. Please, help me to change
> this program so that this is the case.

Well, with you current definition of GExtra.plot_canvas, the type
GExtra.plot_canvas and GObj.widget are equal, so there is no problem.
You could define the plot_canvas function as

let plot_canvas width heigth magnification ?packing ?show () : plot_canvas =
  let w = PlotCanvas.new_plot_canvas width heigth magnification in
    GObj.pack_return (new plot_canvas w) ~packing ~show

if you realy want ocaml to use your type.