[antlr-interest] Predicate Syntax Problem

Terence Parr parrt at cs.usfca.edu
Fri Jan 12 11:45:09 PST 2007


> I'll try the latest jar. I want to validate, but having slept on it  
> I'm not sure what the advantage of putting this in the parser  
> itself is. What I do is build an AST that I pass to a code  
> generator (just some Java code that uses StringTemplate directly,  
> and that code generator could do the same validation, print out  
> nice error messages, kill the build, etc. I get the feeling there's  
> some cool way to use StringTemplate with ANTLR 3 that I don't know  
> about. If there is and there's some documentation somewhere, please  
> point me to it.

Yeah I like doing validation in random java code not with sem preds.

doc: http://www.antlr.org/wiki/display/ANTLR3/Template+construction

You can use -> template construction in either parser or tree  
parser.  There's a new undocumented mode (only in book so far) called  
rewrite=true that uses templates to update the input token buffer in- 
place.  you can then just toString the buffer to see the altered  
buffer. :)  Probably not what you want in this case...

> I thought in the ANTLR 2 docs that validation predicates went *not*  
> on the left. I've been trying to guess how ANTLR 3 works from  
> ANTLR2 docs.

Actually all preds validate but some get hoisted to disambiguate. :)

> Thanks. Really great stuff. I'm just quite the newbie.

Great!


Ter


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