ANTLR : '^' came as a complete surprise to me

Question

I want to set root for AST in this grammar:

boolexp     : relexp op=(AND | OR)^ boolexp
        | relexp
        ;

but get this error:

'^' came as a complete surprise to me

What is the cause?

What exactly surprised you? What did you expect to see? What did you actually see? — George Stocker, Jun 21 '14 at 13:17
@GeorgeStocker, it's [the actual error message ANTLR returns](https://github.com/antlr/antlr4/blob/274120c2b6ea059ad8e9538103163667d2575a2c/tool/src/org/antlr/v4/parse/ToolANTLRParser.java#L69) :) — Bart Kiers, Jun 21 '14 at 13:21
@user3758844, you can't: http://stackoverflow.com/questions/23084533/how-to-generate-ast-in-antlr4 — Bart Kiers, Jun 21 '14 at 13:24

score 0 · Answer 1 · answered Jun 21 '14 at 12:36

0

If this is ANTLR 4, the AST operators have been removed in favor of automatic parse tree construction.

If this is ANTLR 3, you may need to move your labels inside the parentheses, like the following.

boolexp     : relexp (op=AND | op=OR)^ boolexp
        | relexp
        ;

answered Jun 21 '14 at 12:36

Sam Harwell

So how should set root and create Visual AST?It is version 4; – user3758844 Jun 21 '14 at 12:46

1 Answers1