[grammarians] Comparison to RubyFront grammar

[Xue Yong Zhi]

>Nick Sieger and I (well, mostly Nick) were looking at the XRuby grammar at 
>RubyConf. We generated a Java parser and compared it with our current YACC 
>(Jay) based version. It wasn't much faster, unfortunately, but it would be 
>much easier to work with and use for other projects. In addition, it avoids 
>our hand-written (ported from C) lexer, which is a nasty bit of code. We 
>did not do anything to confirm it was parsing correctly, however, so that 
>would probably be the next step.

Antlr is not famous for its speed:) In fact, quite a few folks from yacc 
backgound are disappointed by its speed. Antlr v3 seems to be faster.

>Nick made a few minor changes to the XRuby grammar and got it to work with 
>AntlrWorks, which is Antlr v3-based. I do not believe he tried to generate 
>a parser with v3.

I would like to do a v3 parser, but won't start myself unless v3 is out of 
beta and has documentation ready. Terence(ANTLR's dictator) is very quiet 
since school started, so it does not look like he is going to finish 
something soon. If everyone else want to do it I would be very happy to 
help.

>
>Others do not believe there is value in JRuby pursuing a change of grammar 
>or parser at this time. I believe they are wrong, so I'm very interested. 
>Even if the resulting parser was inappropriate or too much work to use for 
>JRuby at runtime, it would still be useful for IDE work, compiler work, 
>etc.
>

I agree, and will be very glad to see rubyfront is useful for other people. 
I always want to document more about the tricks of parsing ruby, but do not 
have time:( So if anyone has any questions just shoot me an email.

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