[antlr-interest] Faster expression parsing

[Terence Parr]

Heh, really cool!  This is a similar approach to:

http://www.antlr.org/wiki/display/~admin/2008/03/23/Faster+expression 
+parsing+for+ANTLR

except that you do the appropriate tree construction and after parsing  
without consideration of operator precedence. Interesting. I wonder  
which is faster.

Note that you can improve the speed slightly when you are grammar by  
removing unnecessary tree stuff.

> primary_expression
>         :       INTEGER
>                 -> ^(INTEGER)
>         |       '(' expression ')'
>                 -> expression
>         ;

primary_expression
         :       INTEGER
         |       '(' expression ')' -> expression
         ;

Let me know if that makes a difference.

Ter