ANTLR4 mutually left-recursive error

Asked Sep 10 '16 at 09:58

Active Sep 10 '16 at 10:18

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I currently do a recognizer in ANTLR4 and I have an error:

The following sets of rules are mutually left-recursive [expr, index_expr, member_acc, expr1]

This is my code:

num_opds: INTLIT|FLOATLIT;
bool_opds: TRUE|FALSE;
str_opds: STRINGLIT;
operators: ADD|SUB|MUL|DIV|MOD|EQUAL;
expr: <assoc=left> (<assoc=right> (ADD|SUB|NOT)? expr1) (operators (<assoc=right> (ADD|SUB|NOT)? expr1))*;
expr1: (LB expr RB)|ID|num_opds|bool_opds|str_opds|index_expr|member_acc;
index_expr: expr LSB expr RSB;
member_acc: expr DOT ID (LB expr RB)?;

Lexer Token:

LB: '(';
RB: ')';
LSB: '[';
RSB: ']';
DOT: '.';
NOT: '!';
EQUAL: '==';

How can I fix this error ?

edited Sep 10 '16 at 10:18

asked Sep 10 '16 at 09:58

Alex

And your question is...? The error is pretty clear. Refactor your grammar to eliminate the left-recursion, or merge the rules, as ANTLR4 supports direct left-recursion. – Lucas Trzesniewski Sep 10 '16 at 10:11
can you give me a hint? I kinda run into a dead-end in solving this problem. – Alex Sep 10 '16 at 10:17
*The Definitive ANTLR4 Reference*, page 73. Almost exactly your case. – Yuri Steinschreiber Sep 10 '16 at 11:40
I've found my answer, thank you Lucas Trzesniewski and Yuri Steinschreiber – Alex Sep 10 '16 at 14:23

ANTLR4 mutually left-recursive error

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