[antlr-interest] ANTLR itself written using treewalkers?

Loring Craymer lgcraymer at yahoo.com
Fri Nov 3 10:18:08 PST 2006



--- Andy Tripp <antlr at jazillian.com> wrote:
> Trying to grok the overall structure of ANTLR
> itself...my first question...
> 
> ANTLR2 itself doesn't seem to use a treewalker. Why
> not?

Ter was in the midst of starting a company and did the
high-level design and some of the new feature
implementation for ANTLR 2; John Lilley did much of
the grunt work to translate antlr (parser generator)
and sorcerer (tree walker generator; late addition to
PCCTS) code from PCCTS to ANTLR 2.0.  There is a
heterogeneous tree internal to ANTLR 2 which is
converted to a graph, but that was done manually
rather than with a tree walker as a direct
transliteration of antlr internals.  [In other
words,the lack of tree walkers is not by design but by
an accident of historical necessity.]

ANTLR 3 uses tree walkers, although the 3.0 tree
grammars have some defects.  Rewriting ANTLR 3 in
ANTLR will help.

> 
> And is there any sort of description of the internal
> design of ANTLR 
> itself,
> or do I need to just start at Tool.java and drill
> down?

"Abandon hope all ye who enter here."  The internals
of ANTLR 2 are _messy_!

--Loring

> 
> Andy
> 
> 



 
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