Trouble Defining an Object

Trouble Defining an Object

[Paul Snively]

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Folks,

I'm trying to define a class that, given a string containing bytes  
from, e.g. an MP3, Ogg Vorbis, etc. music, contains that music.  
Later, of course, I'll make the class actually do something with the  
data, but for right now I can't even get the code to compile. I'm  
using the current ocamlsdl and findlib. Here's a copy of my session  
in the ocamlsdl toplevel:
- ----------------------------snip snip----------------------------
         Objective Caml version 3.08.4

# #require "sdl.sdlmixer";;
/usr/local/lib/ocaml/site-lib/sdl: added to search path
/usr/local/lib/ocaml/site-lib/sdl/sdlmixer.cma: loaded
# open Sdlmixer;;
# open Filename;;
# class foo init_song =
   let name, chan = open_temp_file ~mode:[Open_binary] "foo" "bar" in
     output_string chan init_song;
     close_out chan;
     let the_song = load_music name in
       object
     val mutable song = the_song
       end;;
               Characters 123-124:
       output_string chan init_song;
                                   ^
Syntax error
- ----------------------------snip snip----------------------------

I'm at a loss to understand where the error lies. Any advice would be  
greatly appreciated.

Many thanks and best regards,
Paul

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Re: [Caml-list] Trouble Defining an Object

[Gerd Stolpmann]

That's a purely syntactic issue. Instead of

class foo =
  expr1;
  expr2;
  object ... end

use:

class foo =
  let () = expr1 in
  let () = expr2 in
  object ... end

Only "let var = expr in expr" may be used between "class" and "object".

Gerd

Am Donnerstag, den 08.09.2005, 11:12 -0700 schrieb Paul Snively:
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> Hash: SHA1
> 
> Folks,
> 
> I'm trying to define a class that, given a string containing bytes  
> from, e.g. an MP3, Ogg Vorbis, etc. music, contains that music.  
> Later, of course, I'll make the class actually do something with the  
> data, but for right now I can't even get the code to compile. I'm  
> using the current ocamlsdl and findlib. Here's a copy of my session  
> in the ocamlsdl toplevel:
> - ----------------------------snip snip----------------------------
>          Objective Caml version 3.08.4
> 
> # #require "sdl.sdlmixer";;
> /usr/local/lib/ocaml/site-lib/sdl: added to search path
> /usr/local/lib/ocaml/site-lib/sdl/sdlmixer.cma: loaded
> # open Sdlmixer;;
> # open Filename;;
> # class foo init_song =
>    let name, chan = open_temp_file ~mode:[Open_binary] "foo" "bar" in
>      output_string chan init_song;
>      close_out chan;
>      let the_song = load_music name in
>        object
>      val mutable song = the_song
>        end;;
>                Characters 123-124:
>        output_string chan init_song;
>                                    ^
> Syntax error
> - ----------------------------snip snip----------------------------
> 
> I'm at a loss to understand where the error lies. Any advice would be  
> greatly appreciated.
> 
> Many thanks and best regards,
> Paul
> 
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> Version: GnuPG v1.4.1 (Darwin)
> 
> iEYEARECAAYFAkMgfwcACgkQO3fYpochAqKSnQCgtaAHbn6WNPyBf5dymt+E2l8n
> IzEAoIzGA4Xb5igB719KOf/msuEBG/wD
> =HlQ/
> -----END PGP SIGNATURE-----
> 
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-- 
------------------------------------------------------------
Gerd Stolpmann * Viktoriastr. 45 * 64293 Darmstadt * Germany 
gerd@gerd-stolpmann.de          http://www.gerd-stolpmann.de
Telefon: 06151/153855                  Telefax: 06151/997714
------------------------------------------------------------

Re: [Caml-list] Trouble Defining an Object

[Jon Harrop]

On Thursday 08 September 2005 19:12, Paul Snively wrote:
> # #require "sdl.sdlmixer";;
> /usr/local/lib/ocaml/site-lib/sdl: added to search path
> /usr/local/lib/ocaml/site-lib/sdl/sdlmixer.cma: loaded
> # open Sdlmixer;;
> # open Filename;;
> # class foo init_song =
>    let name, chan = open_temp_file ~mode:[Open_binary] "foo" "bar" in
>      output_string chan init_song;
>      close_out chan;
>      let the_song = load_music name in
>        object
>      val mutable song = the_song
>        end;;

Perhaps you want:

class foo init_song =
  let name, chan = open_temp_file ~mode:[Open_binary] "foo" "bar" in
  let () =
    output_string chan init_song;
    close_out chan in
  let the_song = load_music name in
object
  val mutable song = the_song
end;;

or even:

let foo init_song =
  let chan = open_out "foo" in
  let () =
    output_string chan init_song;
    close_out chan in
  let the_song = load_music name in
object
  val mutable song = the_song
end;;

But I'm not sure...

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
Objective CAML for Scientists
http://www.ffconsultancy.com/products/ocaml_for_scientists