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Question

I've build a grammar in antlr4 for json-like language.

Gramar file: https://github.com/antlr/grammars-v4/tree/master/json

How would I traverse the tree with Visit function? So far I have code bellow, which outputs stream of tokens, but I would have to parse it again with regex rules, to get members and values.

public void Visit(IParseTree tree)
    {
        for (int i = 0; i < tree.ChildCount; i++)
        {
            if (tree.GetChild(i).ChildCount > 0)
            {
                Visit(tree.GetChild(i));

            }
            else
            {
                Console.WriteLine(tree.GetChild(i).ToString());
            }
        }
    }

I get tree with:

        GramatikaLexer lexer = new GramatikaLexer(inputStream);
        CommonTokenStream commonTokenStream = new CommonTokenStream(lexer);
        GramatikaParser parser = new GramatikaParser(commonTokenStream);

        IParseTree tree = parser.start(); // start is entry point in .g4 file

Answer 1

There should be a GramatikaParserBaseVisitor<T> somewhere around which can be used as a base class.

You can then override the virtual functions like (here: T == object ) object VisitStart(StartContext context) , whose argument has a richer interface than IParseTree and you can access the children by name and they are also typed , ie of type <Child>Context instead of merely IParseTree .