Re: Lua 5 Grammar update

[whisper@...]

Klaas-Jan Stol wrote:

> Hi,
>
> for sake of completeness, I just updated the Lua wiki with a link to a 
> Lua 5 grammar for Bison (or Yacc). I'm using this grammar in my 
> attempt to write a Lua compiler targeting Parrot, the new virtual 
> machine for Perl6. I'm pretty sure it's complete. Lua has 1 ambiguity, 
> as described in the reference manual, this same ambiguity is also 
> present in this grammar file. In this file, it is present as a 
> shift/reduce conflict, resolved by default by a "shift". Adding a 
> semicolon will result in a "reduce". (this is pretty much the same 
> behaviour as in original Lua, I think).
>
> kind regards,
>
> klaas-jan stol
If you want a fast Lua parser (compared to a Yacc-ish one), consider 
PCCTS. It integrates the Bison/Flex syntaxing too. PCCTS can build a 
parser that's comperable in performance to a hand coded top down 
recursive parser.

In contrast to Yacc solutions, it does require a LR parser, not an LALR 
like Yacc. In LR grammars, the repetitions are on the left, not the 
right, ie: expressions, expression, not expression, expressions. (Just 
an abstract example because I'm too lazy to go find a real one... ;-) )

PCCTS is free and open source. Builds on standard C. 
http://www.polhode.com/pccts.html

Very highly recommended!

Dave LeBlanc
Seattle, WA USA