Tutorial for walking ANTLR ASTs in C#?

Question

Is anyone aware of tutorials for walking ANTLR-generated ASTs in C#? The closest I was able to find is this, but it's not terribly helpful.

My goal is to walk through trees that I'm generating based on a domain-specific language that I'm working on, and to use the trees to output generated C# code.

A Java-based tutorial would be helpful, too -- anything that provides clear examples of how to traverse ANTLR ASTs.

Answer 1

I managed to figure this out by adapting the example at the end of Manuel Abadia's article.

Here's my version, which I happen to be using to convert parsed code to C#. These are the steps:

1. Instantiate an ANTLRStringStream or subclass with your input (it can be a file or string).
2. Instantiate your generated lexer, passing in that string stream.
3. Instantiate a token stream with the lexer.
4. Instantiate your parser with that token stream.
5. Get the top-level value from your parser, and turn it into a CommonTree.
6. Traverse the tree:

To get the literal text of a node, use node.Text. To get the token name of a node, use node.Token.Text.

Note that node.Token.Text will only give you the actual name of your token if it's an imaginary token with no corresponding string. If it's a real token, then node.Token.Text will return its string.

For example, if you had the following in your grammar:

tokens { PROGRAM, FUNCDEC }  EQUALS : '=='; ASSIGN : '='; 

Then you'll get "PROGRAM", "FUNCDEC", "==", and "=" from the corresponding accesses of node.Token.Text.

You can see part of my example below, or you can browse the full version.

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public static string Convert(string input) {     ANTLRStringStream sStream = new ANTLRStringStream(input);     MyGrammarLexer lexer = new MyGrammarLexer(sStream);      CommonTokenStream tStream = new CommonTokenStream(lexer);      MyGrammarParser parser = new MyGrammarParser (tStream);     MyGrammarParser.program_return parserResult = parser.program();      CommonTree ast = (CommonTree)parserResult.Tree;      Print(ast);     string output = header + body + footer;      return output; }  public static void PrintChildren(CT ast) {     PrintChildren(ast, " ", true); }  public static void PrintChildren(CT ast, string delim, bool final) {     if (ast.Children == null)     {         return;     }      int num = ast.Children.Count;      for (int i = 0; i < num; ++i)     {         CT d = (CT)(ast.Children[i]);         Print(d);         if (final || i < num - 1)         {             body += delim;         }     } }  public static void Print(CommonTree ast) {     switch (ast.Token.Text)     {         case "PROGRAM":             //body += header;             PrintChildren(ast);             //body += footer;             break;         case "GLOBALS":             body += "\r\n\r\n// GLOBALS\r\n";             PrintChildren(ast);             break;         case "GLOBAL":             body += "public static ";             PrintChildren(ast);             body += ";\r\n";             break;        ....     } }