using System;
// So I can add new visitors without breaking the oop design, but what
// about a new kind of student?

public class weirdstudent: stubase, student
{
  public int weirdness;  // degree of weirdness
  public weirdstudent(string n, int w, student nx): base(n,0,nx)
  {
     weirdness = w;
  }
  public object accept(svisitor v) 
  {
    if (v is wsvisitor) return ((wsvisitor)v).visit(this);
    else throw new Exception("this visitor can't visit a weird student");
  }
}// weirdstudent

// note: in order to add a weirdstuent to a list of students, it must 
// implement interface student.  But svisitor doesn't even know HOW
// to visit a weirdstudent.

public interface wsvisitor : svisitor  // can also visit weird students
{
   object visit(weirdstudent x);
}

// extend auditor lister so it can also visit weirdstudents
public class wauditor : auditor, wsvisitor
{
  public wauditor(student s) : base(s) {}
  public object visit(weirdstudent x)
  {
      Console.WriteLine(x.name+" has gpa 0 but weird students are exempt from probation");
      current = x.next; return null;
  }
}

// alternative to having weirdstudent implement student is to use an
// object adapter

// public class weirdstudent : stubase ...
public class sadapter : student
{
   weirdstudent w;
   public sadapter(weirdstudent x) {w=x;}
   public object accept(svisitor v)
   {
     if (v is wsvisitor) return ((wsvisitor)v).visit(w);  
     else Console.WriteLine("this visitor can't visit weirdos");
     return null;
   }
}

// to add a weird student to a list of normal students, must use adapter:
// student x = new sadapter(new weirdstudent("dod",30000,a)); 

/*
    Compile into stu13b.dll with csc /t:library stu13b.cs /r:stu13.dll
*/