[antlr-interest] Diference bettew Tokens and Lexical Rules

[John B. Brodie]

Greetings!

On Wed, 2010-08-11 at 22:57 -0300, Victor Giordano wrote:
> Hi there!!. How you doing guys? Hope good!.

I am fine, I hope you are too!

> A have another question about tokens and lexical rules, i really don't 
> get the idea...
> For example, assume we have this:
> 
> 1)
> tokens
> {
> 	PLUS= '+';
> }
> 
> 2) PLUS : '+';
> 
> and then a rule
> expr: INT (PLUS INT)*;
> 
> so... if a use one of another is exactly the same. The parse tree is the 
> same, and the generated AST is also the same.
> Can you help me, and try to explain it to me. I read the book, but i 
> don't understand.
> 

As you have discovered, in this instance, ANTLR has 2 ways to express
the same concept.

There is, I believe, nothing else to explain here. You have correctly
analyzed that specifying a string value in the tokens{} block is
equivalent to specifying a lexical rule. Not a problem.

Perhaps I have mis-understood your question, please try to re-state your
question if you are still confused by these two equivalent
meta-syntactic constructs.

Hope this helps...
   -jbb