[antlr-interest] Article against TreeWalkers

[Andrew Bell]

On 3/9/06, mental at rydia.net <mental at rydia.net> wrote:
> Quoting Andrew Bell <andrew.bell.ia at gmail.com>:
>
> For example:
>
>  a : A B C ;
>
> could (notionally) be written:
>
>  a : A NEXT B NEXT C NEXT ;
>
> NEXT simply indicates the normal behavior of advancing to the next
> token.
>
> However, when your tokens happen to be nodes in a tree, there are
> additional navigation possibilities.  You could still use NEXT to
> advance to the next sibling token (i.e. node), but you also have:
>
>  * UP - moves to the parent of the current node
>
>  * DOWN - moves to the first child of the current node
>
> This is a bit like the way that zippers unravel a tree into a
> sequence of navigation operations, though through a different axis.

I guess I wasn't clear.  Aren't we still talking about parsing a text
stream?  Or are we parsing something else -- some data structure that
is in the form of a tree.

--
Andrew Bell
andrew.bell.ia at gmail.com