[antlr-interest] Why no links to ANTLR 3.0 on www.antlr.org??
parrt at cs.usfca.edu
Sat Jun 4 17:11:55 PDT 2005
On Jun 4, 2005, at 1:47 AM, Gerald B. Rosenberg wrote:
> I will try to take a constructive stab at this. Given that the
> problem space and tool are respectively very complex and capable of
> very complex operation, the documentation is just too eager.
I assume you meant "meager" ;)
> It presents something basic and then jets off mixing a bunch of
> fairly complex potential uses together which makes following and
> understanding any one very difficult.
> For example, under http://www.antlr.org/doc/trees.html#_bb4, there
> is brief introduction to marking lexer tokens as roots. Ok. Then
> some stuff about building trees. Nothing there about parser tokens
> as roots.
Apparently the doc is worst than that! What do you mean by parser
tokens? Do you mean imaginary tokens inserted by the parser for
which no actual input lexeme exists?
> I think that is what I need for my problem -- I need to
> understand better how ANTLR wants to mark and construct parser
> trees. So, is marking a new parser token as a root even possible?
> Well, keep looking down. Token translation. Ok. Token
> factories. Ok, I guess. Heterogeneous ASTs. Ok, real advanced.
> Fairly certain that is not applicable to my initial needs.
Interesting...define parser token for me and I'll try to help.
> Finally! An first example ("An Expression Tree Example"). Maybe
> that will walk me through enough to understand how ANTLR wants me
> to solve my problem.
> Problem statement: a simple value accumulator implemented using a
> simple tree. Ok, not really close to my case I think, but sounds
> like it has a similar level of complexity so I should be able to
> learn bunches from it.
> OH, NO: Third paragraph, the "formal statement of the explanation
> of the solution to follow":
> "The AST operator nodes must combine the results of computing the
> value of their two subtrees. They must perform a depth-first walk
> of the tree below them. For fun and to make the operations more
> obvious, the operator nodes define left() and right() instead,
> making them appear even more different than the normal child-
> sibling tree representation. Consequently, these expression trees
> can be treated as both homogeneous child-sibling trees and
> heterogeneous expression trees."
> ??? Fun and obvious??? Make them appear more different??? A
> straight first example? No. More accurately an advanced
> transvestite example.
Did any of the examples or tutorials help? The doc is not
> There are so many issues working in this example, I challenge
> anyone not already an expert to readily tell what design features
> pertain to what -- what is there for fun and what select parts are
> essential for the particular purposes relevant to a relative new-
> comer's basic issues of understanding. The question is, would
> someone not capable of authoring this example in the first place,
> now understand matters well enough to go back and author the
> simple, straight-forward version?
Sounds like we have a navigation issue not doc issue (though I plan
on fixing the doc). Did you see my course notes and all that jazz?
> Now, don't get me wrong: I am not advocating plodding
> documentation. Enthusiasm is a great tool for maintaining interest
> in the narrative, particularly on paper. There just needs to be
> something of a middle ground (at least for us middle of the road
Can you lay out precisely what you've read / looked at what you
haven't? That will tell me a lot! As I say, it may be simply that
the information is not available in the proper order or even defined
in what order you should look.
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