[antlr-interest] simple arithmetic counter

[Tobias Wunner]

Hello,

I am a absolute beginner to ANTLR. I already worked through some  
tutorials but couldn't solve my problem. I would like to add some  
numbers encoded by strings and print them to STDOUT or display them in  
the ANTLR Debug environment (to test if my calculations were correct).  
Two things I didn't find out:

how to display or print out used variables
how to use a global variable as a counter and inrease it e.g. cnt+=a

To start I found a simple grammar for chemical terms beeing able to  
calculate the weight of things like "H2O" or "Cl2".

file :	species*;
species	:	atom DIGITS? {};
atom returns [double weight]
	: 'H' { $weight = 1.00794; }
	| 'C' { $weight = 12.001; }
	| 'Cl' { $weight = 35.453; }
	| 'O' { $weight = 15.999; }
	| 'S' { $weight = 32.06; }
	;
DIGITS	:	('0'..'9');

How could I embed a simple counter? For the beginning I would be happy  
to sum up the weights ignoring the digits (e.g. H20 => 17.00694) How  
can I display the result of the calculations in the debug environment?

For any help I would be gladful!

Regards,
Toby 
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