I'm thinking about using ANTLR in my lecture on formal languages since it's input language is pretty clean and easy to learn. Since I am not an expert using ANTLR I tried some standard examples to get familiar with it's syntax, error messages etc. Doing so I found out, that:
lexer grammar KFG;
R : 'a'R'b' | 'ab';
is a valid lexer that can be executed e.g. by:
echo "aaabbb" | grun KFG tokens -tokens
Since the grammar is context free it should only be parsable by a parser an not a lexer.
Is there any way to force ANTLR to accept only type 3 grammars for lexers?
Cheers, Alex
