Question

How do I write following BNF Grammar in ANTLR?

literal = "{" number "}" CRLF *CHAR8
        ; Number represents the number of CHAR8s

For example {6}\r\nLENGTH should be mapped to "LENGTH" string.

Will following work?

literal: 
   | '{' ('0'..'9')+ '}\r\n'  
        {  
            // C# Code for Lexer
            Text = Text.Trim();
            int n = int.Parse(Text.Substring(1,Text.Length-2));
            Text = "";
            for(int i=0;i<n;i++){
               input.Consume();
            }            
        }
  ;

I am getting this working as a Lexer rule, but problem is I am getting mismatched token, I am not getting token as literal.

Answer 1

This solution works correctly,

literal: 
   | '{' ('0'..'9')+ '}\r\n'  
        {  
            // C# Code for Lexer
            Text = Text.Trim();
            int n = int.Parse(Text.Substring(1,Text.Length-2));
            Text = "";
            for(int i=0;i<n+1;i++){
               Text += (char) input.LA(1);
               input.Consume();
            }            
        }
  ;

Text += (char)input.LA(1); was missing and for some reason, we have to count i from 0 to n+1.