"Expected EOF" error in custom compiler

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C#

compiler

so I am making my own compiler in C# for a custom Language called algebra.
I am following this tutorial http://msdn.microsoft.com/en-us/magazine/cc136756.aspx

Here is the source code of the compiler.
I think there is something wrong with the compiler code.
The code is quite big so I attach it as download links, if you don't want to download them you can look at the tutorial code as the code I have is basically the same.



https://www.dropbox.com/s/6h5fu7f6in3mtfw/Ast.cs
https://www.dropbox.com/s/lt6x8zjltq68q50/Parser.cs
https://www.dropbox.com/s/h84crc42472773s/Program.cs
https://www.dropbox.com/s/gkw2im5n1it28pb/Scanner.cs
https://www.dropbox.com/s/0gnx65to6pfna0y/CodeGen.cs


Here is the code that creates the message(Parser.cs):

public Parser(Collections.IList<object> tokens)
  {
      this.tokens = tokens;
      this.index = 0;
      this.result = this.ParseStmt();

      if (this.index != this.tokens.Count)
          throw new System.Exception("expected EOF");
  }

This code scans for any operator signs(taking '+' as an example)(scanner.cs)
there is more code to this by the way.

case '+':
                input.Read();
                this.result.Add(Scanner.Add);
                break;

This bit is just an enumeration(Ast.cs)

// <bin_op> := + | - | * | /
public enum BinOp
{
Add,
Sub,
Mul,
Div
}

CodeGen.cs

private void GenExpr(Expr expr, System.Type expectedType)
  {
      System.Type deliveredType;

      if (expr is StringLiteral)
      {
          deliveredType = typeof(string);
          this.il.Emit(Emit.OpCodes.Ldstr, ((StringLiteral)expr).Value);
      }
      else if (expr is IntLiteral)
      {
          deliveredType = typeof(int);
          this.il.Emit(Emit.OpCodes.Ldc_I4, ((IntLiteral)expr).Value);
      }
      else if (expr is Variable)
      {
          string ident = ((Variable)expr).Ident;
          deliveredType = this.TypeOfExpr(expr);

          if (!this.symbolTable.ContainsKey(ident))
          {
              throw new System.Exception("undeclared variable '" + ident + "'");
          }

          this.il.Emit(Emit.OpCodes.Ldloc, this.symbolTable[ident]);
      }

  else if (stmt is Print)
      {

These are the 'write' and 'read' statements

// the "write" statement is an alias for System.Console.WriteLine.
           // it uses the string case
           this.GenExpr(((Print)stmt).Expr, typeof(string));
           this.il.Emit(Emit.OpCodes.Call, typeof(System.Console).GetMethod("WriteLine", new System.Type[] { typeof(string) }));
       }

       else if (stmt is ReadInt)
       {
           this.il.Emit(Emit.OpCodes.Call, typeof(System.Console).GetMethod("ReadLine", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Static, null, new System.Type[] { }, null));
           this.il.Emit(Emit.OpCodes.Call, typeof(int).GetMethod("Parse", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Static, null, new System.Type[] { typeof(string) }, null));
           this.Store(((ReadInt)stmt).Ident, typeof(int));
       }

more code here that defines variables ,expressions etc.

/* <expr> := <string>
    *  | <int>
    *  | <arith_expr>
    *  | <ident>
    */
   public abstract class Expr
   {
   }

   // <string> := " <string_elem>* "
   public class StringLiteral : Expr
   {
    public string Value;
   }

   // <int> := <digit>+
   public class IntLiteral : Expr
   {
   public int Value;
   }

   // <ident> := <char> <ident_rest>*
   // <ident_rest> := <char> | <digit>
   public class Variable : Expr
   {
   public string Ident;
   }

   // <bin_expr> := <expr> <bin_op> <expr>
   public class BinExpr : Expr
   {
   public Expr Left;
   public Expr Right;
   public BinOp Op;
   }

More on the operators (scanner.cs)

#region ArithmiticConstants

// Constants to represent arithmitic tokens. This could
// be alternatively written as an enum.
public static readonly object Add = new object();
public static readonly object Sub = new object();
public static readonly object Mul = new object();
public static readonly object Div = new object();
public static readonly object Semi = new object();
public static readonly object Equal = new object();

#endregion

the problem looks like it's not possible to perform any mathematical operations on either a number or variable.

so for example I write such code and try to compile it however I get an error(expected EOF):

variable x = 9;
variable y = 10;
variable ans = x * y;
write ans;

here the output should be 90 however the compiler gives an error 'EOF expected'
However this works:

variable x = 9;
write x;

so I can confirm the language works



I would be very grateful if anyone could help me.
So I appreciate any help that I get. Thanks :)