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.
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:
CommonTree
.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.
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;
....
}
}