ANTLR on a noisy data stream

Question

I\'m very new in the ANTLR world and I\'m trying to figure out how can I use this parsing tool to interpret a set of \"noisy\" string. What I would like to achieve is the follow

Answer 1

You could create only a couple of lexer rules (the ones you posted, for example), and as a last lexer rule, you could match any character and skip() it:

VERB            : 'SLEEPING' | 'WALKING';
SUBJECT         : 'CAT'|'DOG'|'BIRD';
INDIRECT_OBJECT : 'CAR'| 'SOFA';
ANY             : . {skip();};

The order is important here: the lexer tries to match tokens from top to bottom, so if it can't match any of the tokens VERB, SUBJECT or INDIRECT_OBJECT, it "falls through" to the ANY rule and skips this token. You can then use these parser rules to filter your input stream:

parse
  :  sentenceParts+ EOF
  ;

sentenceParts
  :  SUBJECT VERB INDIRECT_OBJECT
  ;  

which will parse the input text:

It's 10PM and the Lazy CAT is currently SLEEPING heavily on the SOFA in front of the TV. The DOG is WALKING on the SOFA.

as follows: