Antlr4 C# Application Tutorial/Example

Question

I want to use Antlr4 to parse some files in my C# application. I have been able to generate the parser and lexer files so far given my grammer. Now I would like to use read in the files and apply the parser and lexer to them. I have been searching for documentation on how to do that but I am coming up short. I have found some old examples using previous versions of Antlr but they don't appear to work for Antlr4. Any help would be appreciated. Thanks.

Answer 1

• In Visual Studio, go to Tools -> Extensions and Updates and search the Online section for "ANTLR Language Support" by Sam Harwell. More information can be found on the GitHub project site
  • This does a few things:
    • Adds Templates for the combined grammars.
    • Adds Syntax Highlighting
    • Adds an MSBuild target for the grammar to generate the parser.
• In your solution, set up your project structure like this:
  • Solution
    • GrammarProject
      • Calculator.g4
    • ImplementationProject
      • GeneratedFiles (All files in this folder are added as Links to files located in GrammarProject\obj\Debug)
        • CalculatorBaseListener.cs
        • CalculatorBaseVisitor.cs
        • CalculatorLexer.cs
        • CalculatorListener.cs
        • CalculatorParser.cs
        • CalculatorVistor.cs
      • MyCalcualtorImplementation.cs
• Write and Compile your grammar.
• In your folder for the Links to Generated Files, Right-Click the folder and click Add -> Existing Item
• Browse to Grammar Project\obj\Debug and select all the generated parser files.
• This next step is important. On the Add button there is a little drop-down arrow. Click the drop-down arrow and click "Add As Link".
  • This will add the generated files to the implementation project using a symbolic link instead of a direct copy.
  • This gives the added benefit of not having to remove and re-add the parser files if you have to change your grammar later.
• Once you have gotten this far, then you can inherit from GrammarProject.CalculatorBaseListener or GrammarProject.CalculatorBaseParser depending on what development pattern you have decided to use.

As a side note, "The Definitive ANTLR 4 Reference" by Terence Parr is an excellent resource to understand how ANTLR4 works and the difference development patterns. All the examples are in java, but the concepts apply to both Java and C#.

Answer 2

try with

using (StreamReader fileStream = new StreamReader(fileName)) {
    AntlrInputStream inputStream = new AntlrInputStream(fileStream);

    SearchLexer lexer = new SearchLexer(inputStream);
    CommonTokenStream commonTokenStream = new CommonTokenStream(lexer);
    SearchParser parser = new SearchParser(commonTokenStream);

    parser.RemoveErrorListeners();
    parser.AddErrorListener(new ErrorListener()); // add ours

    parser.root();
}