[antlr-interest] DFA's encoded directly in java bytecodes

[Robert Colquhoun]

At 09:55 AM 27/10/2004, Terence Parr wrote:
>On Oct 26, 2004, at 1:46 PM, Robert Colquhoun wrote:
> > With all the goto'ing I was just wondering if the assembler you have
> > done
> > above implements the bytecode rule "all approaches to a single point
> > must
> > have the same stack"
>
>Well, do you mean that I guarantee/check for this?  nope ;)  My DFA
>code will keep the stack at 0 minus locals / arguments between states.

Ah ok.  Be careful with exceptions, and it can make loops and stuff 
marginally slower as you need to read the working set of vars from locals 
on each cycle.  You also need to remember state for each local var as you 
are jumping around.

Have you got a small example of the DFA you are trying to generate?  No 
need for correct bytecode, just the algorithm/rules are enough...for 
reference i can code it up with my generator for comparison.

> > I was stuck on action code and how to do semantic actions, its easy to
> > do
> > as separate actions but hard to do inline.
>
>True, but you could invoke the javac compiler in tools.jar like a web
>server :)

Why bother with tools.jar?  antlr has java grammar and i have some bytecode 
generating classes all i need is a tree walker to convert them and i can 
then inline them in the class file itself (The bytecode generator i have 
can insert code at arbitrary points in the method being created, ie run 
through the rule doing the bnf and then compile and insert in the java 
source action fragments).

It's not like Sun has legions of minions working on their compiler to make 
it state of the art...for 1.5 cycle i heard they only had one guy working 
on the whole thing!

;-)

I can post these bytecode generating classes if you want, what license are 
you using for antlr 3?

  - Robert



 
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