[antlr-interest] Lexers hoist simple preds now
Terence Parr
parrt at jguru.com
Sat Aug 31 16:27:54 PDT 2002
Folks,
Haven't heard from anybody on my proposal, but I think it's a good idea
so I've implemented it. Works great for the "beginning of line issue."
Python-parsing lovers rejoice!
You can gate rules in/out depending on semantic context now:
A : {pred1}? 'a' ;
Will only be tested upon pred1 by the lexer. In prior versions, it
would enter the rule and then fail (as a validating pred not
disambiguating pred).
NOTE the really cool thing is that the C++ and C# output generators
will not have to be modified because the code generator is called after
I build the internal representation of nextToken rule. :) Woohoo!
Oh...I do not allow multiple alternative preds from same rule to be
hoisted as that requires real hoisting (i.e., pulling syntactic context
along with semantic).
L8R,
Ter
--
Co-founder, http://www.jguru.com
Creator, ANTLR Parser Generator: http://www.antlr.org
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