Re: [Ocaml-lib-devel] Re: Abstract IO

[Yamagata Y. <yor...@mb...>]

From: "Nicolas Cannasse" <war...@fr...>
Subject: Re: [Ocaml-lib-devel] Re: Abstract IO
Date: Sat, 24 Jan 2004 09:55:54 +0100

> > 2) There would be pros and cons, but maybe objects (not abstract
> >    types) are more fitted to channels.  It makes extension easier, for
> >    example.
> 
> I don't see how it makes extension easier.

Subtyping makes it possible that a channel has its own interface, and
still behaves as a basic channel type.  Of course, there is a cost of
more complex typing.
cryptokit(http://pauillac.inria.fr/~xleroy/software.html) and
ocamlnet(http://ocamlnet.sourceforge.net/) make use of OO-channels.

> > 3) I'd like to see filter type.
> 
> Can you explain more ?

I'm thinking of an interface like

val apply_in : ('a, 'b) input -> ('a, 'b, 'c, 'd) filter -> ('c, 'd)
input

val apply_out : ('a, 'b, 'c, 'd) filter -> ('c, 'd, 'x) output -> ('a,
'b, 'x) output

> I thing that it would be nice to add something like a pipe :
> 
> IO.pipe : () -> ('a,'b) input * ('a,'b,unit) output

Unless it launchs new threads each time, (or we implement continuation
in ocaml) this has not much use.  We have to track which inputs
connect which outputs, oterwise the execution is blocked by the lack of
incoming data.