ANTLR expr sample

expr-program.cs

/*
1. Visit http://www.antlr.org/wiki/display/ANTLR3/Antlr3CSharpReleases and download antlr-dotnet-tool-xxx.7z
2. unzip the 7z file.
3. Create solution in Visual Studio and add the following reference for the project: antlr3.runtime.dll.
4. Copy this file as program.cs
5. In unziped files, you can find antlr3.exe.  Use it to generate necessary cs files: antlr3.exe expr.g3.
6. Add generated cs files to project.
7. Create folder 'sample' in the project and add a text file named Expr1.txt
8. Place the follow content in Expr1.txt, then change the property 'Copy to Output Directory' to "Copy always".
1+1
x=2
y=3
x+y
9. Build and run!
*/
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Antlr.Runtime;

namespace expr
{
  class Program
  {
    static int calc(string input)
    {
      ANTLRStringStream stream = new ANTLRStringStream(input);
      var lexer = new exprLexer( stream );
      var tokens = new CommonTokenStream(lexer);
      var parser = new exprParser( tokens );
      var result = parser.expr().value;
      return result;
    }

    static void standardTest()
    {
      ANTLRFileStream input = new ANTLRFileStream("sample\\Expr1.txt");
      var lexer = new exprLexer( input );
      var tokens = new CommonTokenStream(lexer);
      var parser = new exprParser( tokens );
      parser.prog();
      var result = parser.expr().value;
      Console.WriteLine("Result = {0}", result);
    }

    static void Main(string[] args)
    {
      standardTest();
      Console.WriteLine("calc( '1+2' )={0}", calc("1+2"));
      Console.WriteLine("calc( '100+200' )={0}", calc("100+200"));
      Console.WriteLine("calc( '1000+2000' )={0}", calc("1000+2000"));
      Console.WriteLine("calc( '10000+20000' )={0}", calc("10000+20000"));
      Console.WriteLine("Parse done.");
      Console.ReadLine();
    }
  }
}

expr.g3

grammar expr;

options {
    language=CSharp3;
    TokenLabelType=CommonToken;
    output=AST;
    ASTLabelType=CommonTree;
}

@lexer::namespace{expr}
@parser::namespace{expr}

@header {
using System;
}

@members {
/** Map variable name to Integer object holding value */
Dictionary<string, int> memory = new Dictionary<string, int>();
}

public prog:   stat+ ;
                
stat:   expr NEWLINE {Console.WriteLine( "{0}", $expr.value);}
    |   ID '=' expr NEWLINE
        {memory.Add($ID.text, Convert.ToInt32($expr.value));}
    |   NEWLINE
    ;

public expr returns [int value]
    :   e=multExpr {$value = $e.value;}
        (   '+' e=multExpr {$value += $e.value;}
        |   '-' e=multExpr {$value -= $e.value;}
        )*
    ;

multExpr returns [int value]
    :   e=atom {$value = $e.value;} ('*' e=atom {$value *= $e.value;})*
    ; 

atom returns [int value]
    :   INT {$value = Convert.ToInt32($INT.text);}
    |   ID
        {
		int v;
		if( memory.TryGetValue( $ID.text, out v ) )
		  $value = v;
		else
		  Console.WriteLine( "undefined variable {0}", $ID.text );
        }
    |   '(' expr ')' {$value = $expr.value;}
    ;

ID  :   ('a'..'z'|'A'..'Z')+ ;
INT :   '0'..'9'+ ;
NEWLINE:'\r'? '\n' ;
WS  :   (' '|'\t')+ {Skip();} ;