public class Jit<T>
{
  T _instance;
  object[] _ctor_params;

  public Jit(object[] ctor_params)
    {
      _ctor_params = ctor_params;
    }

  public Jit()
    {
    }

  public T create(object[] ctor_params)
    {
      Type[] param_types = ctor_params.Aggregate<object, List<Type>>(
			     new List<Type>(),
			     (List<Type> lt, object o) =>
	                       {
				 lt.Add(o.GetType());
				 return lt;
			       }).ToArray();
      var ctor = typeof(T).GetConstructor(param_types);
      if (ctor == null)
	throw new Exception(param_types.Aggregate<Type, String>(
		      "No constructor found for " + typeof(T).Name + " taking",
         	      (string i, Type t) => { return i + " " + t.Name; }));
      return (T)ctor.Invoke(_ctor_params);
    }

  public T create()
    {
      return (_ctor_params == null)
	? create(new object[] { })
	: create(_ctor_params);
    }

  public T single()
    {
      if (_instance == null)
	_instance = create();
      return _instance;
    }
}