[antlr-interest] Newbie: Is it an ANTLRWorks bug or a feature?

孟岩 myan at csdn.net
Wed Oct 22 06:35:48 PDT 2008

Hi all,

I am learning ANTLR and just joined this mailing list. I don’t know where
to submit bugs, is here the right place?


Anyway, I found something unusual in ANTLRWorks. Consider this grammar:



grammar G;


expr :        INT (('+' INT {System.out.println("matched +");})

                       |('-' INT {System.out.println("matched -");})

                       |('*' INT {System.out.println("matched *");})

                       )* NEWLINE;

INT   :        '0'..'9'+;

NEWLINE :        '\r'? '\n';



In ANTLRWorks 1.2, put this grammar text in the main editor, switch to the
“Interpreter” tab view, input “3+2<Enter>” or “3*2<Enter>” and click
the triangle button, it will show the right tree diagram. Nevertheless, the
“3-2<Enter>” expression will encounter a wrong diagram. I tried several
times, and it turns out that the whatever the second sub-expression will
fail to generate correct tree diagram. 


Is it a bug or a feature?




Mike Meng

October 22, 2008



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