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Message-ID: <16482.33127.497203.821118 at soggy.deldotd.com>
Date: Wed, 24 Mar 2004 22:51:19 -0800
To: lablgtk at kaba.or.jp
Subject: event variant types
From: briand at aracnet.com

Well maybe.  I'm new to ocaml and the type system has got me a bit confused.

Essentially I'd like to create a function and associated variant so
that I can pass multiple event types as one argument:

let fun event = 
  match event with
    mouse_event -> 
  | button_event ->
  | keypress_event -> ;

So I tried a type which looks like :

type an_event = E1 of GdkEvent.Motion.t | E2 of GdkEvent.Key.t | E3 of GdkEvent.Button.t ;;

and a match which looks like

let multi_event_procedure drawv event =
...
    match event with
        E1(event) -> true
      | E2(event) -> true
      | E3(event) -> true;


which is in a routine which is invoked :

        area#event#add [`BUTTON_PRESS];
        w#event#connect#button_press ~callback:
          begin fun ev ->
              multi_event_procedure drawv ev;
              true
          end;

which gives me the error :

This expression has type GdkEvent.Button.t = GdkEvent.Button.types Gdk.event
but is here used with type an_event

Of course I think it should work or I wouldn't be bothering the list  :-)

Any help appreciated.

Thanks


Brian