On Wed, Oct 01, 2008 at 11:24:04PM -0400, Brandon S. Allbery KF8NH wrote:
> On 2008 Oct 1, at 22:23, Timothy S. Nelson wrote:
>> On Wed, 1 Oct 2008, Brandon S. Allbery KF8NH wrote:
>>> On 2008 Oct 1, at 22:14, Timothy S. Nelson wrote:
>>>>    Hi all.  I've enjoyed(?) reading over the February/March thread 
>>>> entitled "Musings on operator overloading".  I've brought a few thoughts 
>>>> along; if they're old news, please tell me
>>>> here to do more reading on it :).
>>> The Perl6 way to do this is grammars; using an XML grammar to pull data 
>>> out of an XML document is one of Larry's favorite examples.
>>      Ok, great.  While I see how this does a great job of converting the 
>> string of data into a plex, it doesn't solve the problem of selecting the 
>> data from the plex in a glob-like (or XPath-like) fashion, which is what 
>> I'm talking about here.  Have I missed something that will do that?
> I could have sworn there was a short and elegant example of using a grammar 
> to extract arbitrary information from an XML document, but I don't see it 
> in the documentation.  I recall Trey Harris showing such an example on IRC 
> but not in a logged channel; maybe he'll see this message and jump in, or 
> if not I'll see if I can get him to write another example.

The key point Brandon is making, that I'm not sure you're answering,
is that he wants to extract elements of a tree-like data structure
(think DOM), not simply from a string representation of a structure
(such as an XML document in a string).

Thinking in terms of grammars, I'd ask the question: could grammars be
used to match tree-like data structures? I think the current answer is no.
Grammars are too tightly bound to the concept of a position in a linear

But I have a nagging suspicion that this is a very powerful idea.
Applying the expressive power of a grammar-like mechanism to
search, backtrack, and match within a tree-like data structure.

Is this new or has anyone discussed it before?


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