Re: Yacc, lex, and C++

From: bill_kempf (williamkempf_at_[hidden])
Date: 2002-02-26 13:04:06

--- In boost_at_y..., Douglas Gregor <gregod_at_c...> wrote:
> On Tuesday 26 February 2002 12:28 pm, you wrote:
> > Doees anyone know of a C++-friendly version of yacc, or, better 
yet, a
> > version of yacc that produces a generic algorithm (e.g., take as 
input a
> > pair of InputIterators)?  Yacc / bison as it stands is quite 
unfriendly to
> > C++, as you cannot put C++ objects on the evaluation stack, which 
means
> > that you can't always get objects properly destroyed.  You can
> > partially get around this by putting only pointers on the 
evaluation
> > stack, and having the code that accompanies a production rule be
> > responsible for managing the objects on which it operates, but 
this scheme
> > breaks down when it comes to error processing -- values get 
popped off of
> > the evaluation stack without giving you any opportunity to 
process them.
> 
> I looked around somewhat recently for the same thing, and was 
unfortunately 
> unable to find any generic parser other than Spirit (which I 
couldn't use 
> only because of the fear of adding yet another library). I ended up 
using 
> Bison with lots of pointers, grumbling all the way...

Did you look at ANTLR? (http://www.antlr.org)

> > The Spirit parser is not what I am looking for, as it is limited 
to
> > recursive-descent parsing, and is hence unsuitable for many 
applications
> > (say, parsing a C++ program).
> 
> As Dave Abrahams already mentioned, several of the better C++ 
parsers uses 
> recursive descent parsing. This is generally because recursive 
descent 
> parsers handle context sensitivity and arbitrary lookahead _much_ 
better than 
> any Yacc-based solution. Check out gcc/cp/parse.y in the GCC source 
code to 
> see all of the ugliness a Yacc-based parser adds; especially look 
at the 
> comments. Also note that there is an experimental recursive descent 
parsing 
> for GCC that will replace the Yacc-based parser in the future.

The ANTLR/PCCTS books have a lot to say about recursive descent 
parsing.

Bill Kempf