[Caml-list] syntax change (was: camlp4o problem)

[Markus Mottl <markus@oefai.at>]

On Mon, 04 Feb 2002, Daniel de Rauglaudre wrote:
> It has no chance to become the standard if nobody wants to use it...

And unfortunately vice versa...

> There are very few users interested in the revised syntax.

Because it is not standard.

> How much do you estimate the chances that people will accept a major
> change of the syntax?

If it breaks their previous work and/or if they cannot continue in their
old style (at least for a while), ...

> You want my opinion? 0%

... then 0%, I agree.

> If you have written an application of 50000 lines of OCaml on 60 files
> in 5 directories, are you accepting that the new version of OCaml has
> a very new syntax, very clean and very incompatible with the previous
> one?

If I can use camlp4 conveniently to work with my existing sources as if
no change had happened, I wouldn't mind, but I fear that not everything
would work smoothly right now. It should at least in principle be possible
(though a lot of work) to design all language tools in such a way that
they accept ASTs annotated with position information (for exact error
messages), thus making them completely independent of concrete syntax.

This would make later syntax changes much less cumbersome for both the
maintainers and the users and allow the language to evolve faster. A
rather strategic proposal for the language and environment...

> And even if you want to convert to it, what is your reaction if the
> new version of OCaml has a bug in a part very important for you?

I don't quite understand this argument: bugs can happen during every
change, what is the problem with syntax changes in particular?

> Well, there is no need to impose a new clean standard syntax, because
> there is Camlp4. If most of people use the revised or any-clean syntax,
> it becomes a standard de facto.

I disagree here. People need a "soft kick" to change. Surely, it shouldn't
be a painful one, this would just drive away users, but a strong enough
one to make them go and give future users of OCaml the opportunity to
start out with an even saner syntax.

> I am ok for a definition of a new syntax. I propose the revised syntax
> as a start of the discussion.

That's ok for me. There may be small details where I could argue about
alternatives, but it is probably a good start.

> I don't propose to start with the normal syntax because it is too much
> difficult to parse with recursive descent technology. I managed to do
> it but thanks to hacks.

Sounds reasonable.  For people who want to learn more about
advantages/disadvantages of LL-parsers (= recursive descent) vs.
LALR-parsers (= ocamlyacc), see this article:

  http://compilers.iecc.com/comparch/article/91-06-032

Regards,
Markus Mottl

-- 
Markus Mottl                                             markus@oefai.at
Austrian Research Institute
for Artificial Intelligence                  http://www.oefai.at/~markus
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