Re: [Caml-list] Camlp4/p5 type reflection [

["Jérémie Dimino" <jeremie@dimino.org>]

Le dimanche 11 décembre 2011 à 12:19 +0100, Gabriel Scherer a écrit :
> If we had no Camlp4, we should push for some of these things to be
> integrated in the language.
> A reasonable but solid mixfix syntax could replace pa_monad, the
> "##"-syntax of pa_js, and some aspects of pa_lwt.
> "jsnew" and list comprehensions could perfectly be handled as quotations.

I don't think it is possible to do pa_lwt via mixfix syntax. For example
pa_lwt does this kind of transformation:

  lwt x = f () and y = g () and z = h () in
  return (x + y + z)

-->

  let t1 = f () and t2 = g () and t3 = h () in
  Lwt.bind t1 (fun x -> Lwt.bind t2 (fun y -> Lwt.bind t3 (fun z -> return (x + y + z))))

The first form is much more readable. And it has another big advantage:
it adds backtrace support. Because as soon as you use monads in ocaml,
backtraces are unusable. And you just can't seriously ask the user to
write that kind of code:

  Lwt.fail (try raise End_of_file with exn -> exn)

So unless we have better support for monads in OCaml itself, i think
Camlp4 is still required.

That said, i am not either a big fan of extending the syntax since it
makes code harder to understand for those who don't know the extensions.

-- 
Jérémie