[antlr-interest] Lexer non-determinism

[seaswar <sje at sigma-inc.com>]

I posted this on the jGuru forum but got no reply. Perhaps I'll have 
better luck here.

I don't understand why the following is ambiguous for k=2 but notfor 
k=3. I checked the generated code (java, antlr 2.7.1) and it looks 
right. So I turned of the warning. But I would still like to 
understand why there is a warning in the first place. No warning is 
generated for k=3.

class TestLexer extends Lexer;

options { k = 2; }

MULTI_LINE_COMMENT
    :    "/*"
         (    { LA(2) != '/' }? '*'
         |    ( "\r\n" | '\n') { newline(); }
         |   ~( '*' | '\r' | '\n')
         )*
         "*/" { $setType(Token.SKIP); }
    ;

ANTLR Parser Generator   Version 2.7.1   1989-2000 jGuru.com
com/qsi/parser/test/test9.g:7: warning: lexical nondeterminism upon
com/qsi/parser/test/test9.g:7:  k==1:'*'
com/qsi/parser/test/test9.g:7:  k==2:'/'
com/qsi/parser/test/test9.g:7:  between alt 1 and exit branch of block



 

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