anything more convenient then bison/yacc?

Hi all,


I am wondering if there are some newer reliable engines
similar to yacc/bison, but with more syntactic sugar and
wider class of the grammars.


In particular some ideas/notions of regular expression
would be fine. For example, something like:


    e? Matches element e in brackets zero or one times
    e* Matches element e in brackets zero or more times
    e+ Matches element e in brackets one or more times
    e{num} Matches element e in brackets num times
    e{min, max} Matches element e in brackets at least min times, but
not more than max times


where element e might be a compound elemnt embraced, say,
in brackets if needed.


Absence of this sugar makes the grammar description
less readable.


Consider this short example (BTW it comes from real life):


[example]
    Rule: [a [b?a]* b? ]?
[/example]


Would it ever be same readable in bison/yacc grammar? -- hardly.


Indeed let's look into intuitive bison equivalent:


[example]
%%
%term a
%term b


Rule:
        | a ba_seq_opt
        | a ba_seq_opt b
        ;


ba_seq_opt:
                    | ba ba_seq_opt
                    ;


ba: a
    | b a
    ;


[/example]




It is hardly more readable and in addition
brings 2 "artificial" shift/reduce conflicts...


Thus, any testimonials to reliable grammar parser generators
are very appreciated. (Commercial implementatios are
less considered). In particular, recommendations to
free implementations from this list:


    http://www.programming-x.com/programming/parser.html


would be very interesting as well.


Best regards,
thank you in advance,
Valery A.Khamenya

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