Re: [Caml-list] quasiquoting: 3 parsers for camlp4 vs 1 for haskell?

[Geoffrey Mainland <mainland@eecs.harvard.edu>]

On Thu, Apr 23, 2009 at 12:19:09AM +0100, Jon Harrop wrote:
> On Friday 17 April 2009 19:24:31 Joel Reymont wrote:
> >  From the quasiquoting paper by Geoffrey Mainland [1], page 7:
> >
> > "The major advantage of our approach over that of camlp4
> > is that we demonstrate how to use generic programming
> > to reuse a single parser to parse quasiquoted patterns,
> > quasiquoted expressions and plain syntax that does not
> > include antiquotes. Because OCaml does not support generic
> > programming out of the box,
> 
> I have no idea what he meant by this.
> 
> > in camlp4 this would require three separate parsers,
> 
> AFAICT, that was not true when he wrote it (Sept 2007) and is not true today.
> 
> > each generating different representations of the same concrete syntax."
> 
> That has never been true.
> 
> > Can someone shed light on how, where and why three different
> > parsers are required for camlp4?
> 
> I've CC'd the author. Perhaps he can shed some light on this.

I actually spoke with Nicolas Pouillard about this at the workshop, and
he informed me that his rewrite of camlp4 for the 3.10 release included
a facility for translating a value into an OCaml AST representing that
value, so yes, that statement is now incorrect. I think Jake Donham's
reply to Joel's message of 4/15 made this clear and even helpfully
pointed to some code.

As for my work, I hope that anyone reading the paper will find the
technique I used to provide this functionality in the Haskell
implementation of quasiquotation both elegant and easy to understand.

Geoff