[antlr-interest] Calling a function on token match

[Burton Samograd]

Hello,

I am trying to call some code every time a token matches ('\n' in this case).  My naive attempt is:

fragment
NEWLINE
    : '\n' { std::cerr << "NEWLINE\n"; }
    ;

Giving:

error(100): SDL.g:0:0: syntax error: buildnfa: <AST>:913:12: expecting EOA, found ' std::cerr << "NEWLINE\n";

I found this related post:

http://www.antlr.org/pipermail/antlr-interest/2009-February/032921.html

But I'm not fluent enough in antlr to understand exactly what the solution entails.  In our grammar we have a number of places to handle whitespace like ( ' ' | '\t' | '\r' | '\n' ) which I am hoping that with the above NEWLINE rule can then be replaced with ( ' ' | '\t' | '\r' | NEWLINE ).  I want to update an external line count variable using a function in the code to be called on token match.

Is what I'm trying to do possible?  If so, could someone show me an example of how to call code on a token match.

Thank you.

--
Burton Samograd

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