Asm{{
  public static void p(String s){ Console.Error.Write(s); }
  /*public static void Main(String[] args){
    if(args.Length == 0){
       p(" ** usage: asm.exe <InputFile>\n");
       return;
    }

    OpList code = Asm.parse(new System.IO.FileStream(args[0],System.IO.FileMode.Open)).c;
    p("\n OpCodes: \n"+code.Print()+"\n");
    List<Entry> labels = code.labels();
    p("\n Eval = "+(code.eval(new ExecStack(labels)).top())+"\n");
  }*/
}}

OpList{{
  public abstract OpList append(Opcode o);
  public abstract OpList append(OpList ol);
  public abstract ExecStack eval(ExecStack s);
  public ExecStack eval(){ return eval(new ExecStack(labels())); }
  public OpList prepend(Opcode o){ return new OpCons(o,this); }
  public List<Entry> labels(){ return labels(new Empty<Entry>()); }
  public abstract List<Entry> labels(List<Entry> e);
}}

OpCons{{
  public override OpList append(Opcode o){ return new OpCons(first, rest.append(o)); }
  public override OpList append(OpList ol){ return new OpCons(first, rest.append(ol)); }
  public override ExecStack eval(ExecStack s){ return first.eval(s,rest); }
  public override List<Entry> labels(List<Entry> e){
    return rest.labels((first is Label)?
           e.push(new Entry(((Label)first).id.ToString(),rest)):e);
  }
}}

OpEmpty{{
  public override OpList append(Opcode o){ return new OpCons(o, this); }
  public override OpList append(OpList ol){ return ol; }
  public override ExecStack eval(ExecStack s){ return s; }
  public override List<Entry> labels(List<Entry> e){ return e; }
}}

Opcode{{
  public abstract ExecStack eval(ExecStack s);
  public virtual ExecStack eval(ExecStack s, OpList cc){ return cc.eval(eval(s)); }
}}

MathOp{{
  public virtual int op(int l, int r){ throw new Exception("NYI Opcode"); }
  public override ExecStack eval(ExecStack s){
    int r = op(s.top(), s.popRes().top());
    return s.popRes().popRes().pushRes(r);
  }
}}

Plus   {{ public override int op(int l, int r){ return l+r; } }}
Minus  {{ public override int op(int l, int r){ return l-r; } }}
Times  {{ public override int op(int l, int r){ return l*r; } }}
Divide {{ public override int op(int l, int r){ return l/r; } }}
Less   {{ public override int op(int l, int r){ return (l<r)?1:0; } }}
Greater{{ public override int op(int l, int r){ return (l>r)?1:0; } }}
Equal  {{ public override int op(int l, int r){ return (l==r)?1:0; } }}
And    {{ public override int op(int l, int r){ return ((l&r&1)==1)?1:0; } }}
Or     {{ public override int op(int l, int r){ return ((l|r&1)==1)?1:0; } }}

Push {{ public override ExecStack eval(ExecStack s){ return s.pushRes(i); } }}
Pop  {{ public override ExecStack eval(ExecStack s){ return s.popRes(); } }}
Def  {{ public override ExecStack eval(ExecStack s){ return s.pushEnv(s.top()).popRes(); } }}
Undef{{ public override ExecStack eval(ExecStack s){ return s.popEnv(); } }}
Load {{ public override ExecStack eval(ExecStack s){ return s.pushRes(s.load(i)); } }}

ControlOp{{
  public abstract String Id();
  public abstract bool branch(ExecStack s);
  public override ExecStack eval(ExecStack s){ return s; }
  public override ExecStack eval(ExecStack s, OpList cc){
      if(branch(s))
          return s.labels.find(new Find(Id())).pc.eval(s);
      return cc.eval(s);
  }
  class Find : List<Entry>.Pred{
      String id;
      public Find(String s){ id = s; }
      public override bool huh(Entry e){ return e.label.Equals(id); }
  }
}}

Label{{
  public override String Id(){ return ""+id; }
  public override bool branch(ExecStack s){ return false; }
}}
Jmp{{
  public override String Id(){ return ""+id; }
  public override bool branch(ExecStack s){ return true; }
}}
IfZ{{
  public override String Id(){ return ""+id; }
  public override bool branch(ExecStack s){ return (s.top() == 0); }
}}

ExecStack{{
  List<int> env = List<int>.create(),
            result = List<int>.create();
  internal List<Entry> labels = List<Entry>.create();

  public ExecStack(List<int> e, List<int> r, List<Entry> l){ env = e; result = r; labels = l; }
  public ExecStack(List<Entry> e){ labels = e; }
  public ExecStack pushEnv(int i){ return make(env.push(i),result); }
  public ExecStack pushRes(int i){ return make(env,result.push(i)); }
  public ExecStack popEnv(){ return make(env.pop(),result); }
  public ExecStack popRes(){ return make(env,result.pop()); }

  public int load(int i){ return env.lookup(i); }
  public int top(){ return result.top(); }
  ExecStack make(List<int> e, List<int> r){ return new ExecStack(e,r,labels); }
  public override String ToString(){
      return "    Env: ["+env+"]\n"+
             "    Res: ["+result+"]\n";
  }
}}