[antlr-interest] Article against TreeWalkers

Terence Parr parrt at cs.usfca.edu
Thu Mar 9 14:22:47 PST 2006

On Mar 9, 2006, at 2:14 PM, Jeff Barnes wrote:

> Andrew sez:
>> You are parsing a 1-D input and producing a tree output, right?  What
>> am I missing here?
> Terence sez:
> <snip> Once you have a
> tree, you need to walk it either by hand or by grammar.  By grammar,
> you can serialize a tree by adding imaginary nodes UP and DOWN that
> encode 2D aspect.
> Jeff sez:
> So, why aren't there UP and DOWN tokens in the tree metalanguage?

They are added for you so you can just give a nice tree grammar like:

expr : ^(PLUS expr expr)
	| INT

> Or am I missing something? Methinks that would coolify a TreeWalker.

Tree grammars are cool :)


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