[antlr-interest] Re: woohoo! ParseTrees for free, Debugging for me!

[lgcraymer]

Ter--

If I interpret this right, you're actually visualizing parse trees 
without generating them.

Modifying ANTLR to build parse trees is even easier--add the root 
node creation code in genRule (XXXCodeGenerator) and modify refRule 
in DefineGrammarSymbols.java, then adding an option recognizer to 
ParserGrammar.java.  About 10-15 lines total, unless I've missed 
something.  


--Loring


--- In antlr-interest at yahoogroups.com, Terence Parr <parrt at c...> 
wrote:
> Howdy,
> 
> I just made ANTLR generate parse trees w/o modifying the tool 
itself.  
> I just overrode match(), traceIn(), traceOut() in the parser and 
turned 
> on -traceParser. :)  Not only will it build a parse tree for you 
to 
> look at, it knows how to dump the derivation tree!  This is super 
great 
> thing for debugging big grammars.  The question is always "how is 
xxx 
> being matched? I know it's not right!"  This derivation tool will 
> pretty much tell you.  For example, here is the output when I 
run "int 
> i;" into a tinyc example with parse tree construction overrides:
> 
> $ java Test < decl.c
> parse tree:  ( <program> ( <declaration> ( <variable> ( <type> 
int ) ( 
> <declarator> i ) ; ) ) EOF )
> derivation:
>      <program>
>   => <declaration> EOF
>   => <variable> EOF
>   => <type> <declarator> ; EOF
>   => int <declarator> ; EOF
>   => int i ; EOF
> 
> pretty cool, n'est-ce pas?  You can see precisely how your input 
is 
> matched by the grammar.
> 
> Note: this is what a parse tree is for...not translation.  For 
that you 
> use an AST or token stream rewriting (got something comin on that 
too). 
> :)
> 
> I'm going to go to the gym and if I have the energy I'll write up 
the 
> mechanism later and post to ANTLR.org.
> 
> Anybody wanna port to C#? ;)  I know somebody that could use it 
about 
> now ;)  Should I roll this into 2.7.3?  Perhaps not as we want to 
> quickly get out a bug fix release w/o having to wait for C++ and 
C# 
> implementations...
> 
> Ter
> --
> Professor Comp. Sci., University of San Francisco
> Creator, ANTLR Parser Generator, http://www.antlr.org
> Co-founder, http://www.jguru.com
> Co-founder, http://www.knowspam.net enjoy email again!
> Co-founder, http://www.peerscope.com pure link sharing


 

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