如何从ANTLR语法中收集“返回”

Question

If I have a ANTLR grammar where I have rules like this with a 'returns' statement:

string_decl returns [Pair s] : STR id EQUAL ex=str_literal ';'{$s = new Pair($id.text, $ex.text);} ;

And then in my main I have code like this:

 Lexer lexer = new Lexer(CharStreams.fromFileName(inputFileName));
 CommonTokenStream tokens = new CommonTokenStream(lexer);
 Parser parser = new Parser(tokens);

 System.out.println(parser.program()); //prints out empty array ?

How do I print out a list of all of my 'returns'?

Answer 1

The returns value is modeled as member of the rule context. See if you have a String_declContext.s member. See also Rule Attribute Definitions in the ANTLR4 documentation.