Re: [Caml-list] Array.make exception and parser

[Francois Pottier <Francois.Pottier@inria.fr>]

On Tue, Jan 04, 2011 at 08:30:48PM +0100, Daniel Bünzli wrote:
> So everybody trades developer convenience for end user convenience --
> I mean, the syntax errors produced by LR parsers are just terrible,

It is true that ocamlyacc (and Menhir) offer essentially no support for
explaining parse errors. (The "error" pseudo-token, inherited from yacc, is
supposed to help, but in my opinion its use pollutes the grammar and makes it
uncontrollable.) Nevertheless, as underlined by Yitzhak, I don't think there
is a deep reason why LR parsers must be bad at explaining errors. In
principle, upon detecting an error, an LR parser could easily dump the stack,
which corresponds to the sentence (composed of terminal and non-terminal
symbols) that has been recognized so far. It could also display the set of
look-ahead tokens that would *not* have caused an error in the current
state. (Come to think of it, this is a feature that I would like to add to
Menhir, if only time was not so much of the essence!)

-- 
François Pottier
Francois.Pottier@inria.fr
http://gallium.inria.fr/~fpottier/