Is it possible to get the "active" ANTLR rule from which a action method was called?
Something like this log-function in Antlr-Pseudo-Code which should show the start and end position of some rules without hand over the $start- and $end-tokens with every log()-call:
@members{
private void log() {
System.out.println("Start: " + $activeRule.start.pos +
"End: " + $activeRule.stop.pos);
}
}
expr: multExpr (('+'|'-') multExpr)* {log(); }
;
multExpr
: atom('*' atom)* {log(); }
;
atom: INT
| ID {log(); }
| '(' expr ')'
;
No, there is no way to get the name of the rule the parser is currently in. Realize that parser rules are, by default, simply Java methods returning a void
. From a Java method, you cannot find out the name of it at run-time after all (when inside of this method).
If you set output=AST
in the options { ... }
of your grammar, every parser rule creates (and returns) an instance of a ParserRuleReturnScope
called retval
: so you could use that for your purposes:
// ...
options {
output=AST;
}
// ...
@parser::members{
private void log(ParserRuleReturnScope rule) {
System.out.println("Rule: " + rule.getClass().getName() +
", start: " + rule.start +
", end: " + rule.stop);
}
}
expr: multExpr (('+'|'-') multExpr)* {log(retval);}
;
multExpr
: atom('*' atom)* {log(retval);}
;
atom: INT
| ID {log(retval);}
| '(' expr ')'
;
// ...
This is however not a very reliable thing to do: the name of the variable may very well change in the next version of ANTLR.