S>>>Значит функции Дирихле тоже нет

8.2.5.1 Identity

The identity operator is defined by the CTS as follows.
• If the values have different exact types, then they are not identical.
• Otherwise, if their exact type is a value type, then they are identical if and only if the bit
sequences of the values are the same, bit by bit.
• Otherwise, if their exact type is a reference type, then they are identical if and only if the
locations of the values are the same. (1)

Identity is implemented on System.Object via the ReferenceEquals method. (2)

S>>ссылка обеспечивает все что нужно, что бы обратится к объекту с identity. Но из этого не следует что из идентичности следует совпадение ссылок. По крайней мере для логической идентичности это не следует (http://c2.com/cgi/wiki?ObjectIdentity).
G>Для конкретного языка — следует, можешь обратный пример привести? Я таких не знаю.
Для C# две строки с одинаковым содержимым.

var sqrt2 = new Sqrt(2);
Assert(sqrt2 * sqrt2 == 2);

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A>>dynamic a = new A {X = 42};
A>>dynamic d = ExposedObject.From(a);
A>>Console.WriteLine(d.X);//42
A>>Console.WriteLine(object.ReferenceEquals(a, d));//false!!!
A>>

class A
{
    public int X { get; set; }

    public override string ToString()
    {
        return string.Format("X = {0}", X);
    }

    public override bool Equals(object obj)
    {
        var o = obj as A;
        return o != null && o.X == X;
    }
}

var a = new A {X = 42};
dynamic o = a;
dynamic ex = ExposedObject.From(o);

Console.WriteLine(ex.X);//42
Console.WriteLine(ex.GetType().GetProperty("X").GetValue(a, null));//42

Console.WriteLine(ex);//X = 42
Console.WriteLine((A)ex);//X = 42

Console.WriteLine(ex.Equals(o));//true
Console.WriteLine(ex.GetType() == a.GetType());//true
Console.WriteLine(ex.GetType() == typeof(A));//true
Console.WriteLine(ex.GetHashCode() == a.GetHashCode());//true

Console.WriteLine(object.ReferenceEquals(a, ex));//false!!!

Console.WriteLine(o is A);//true
Console.WriteLine(o as A != null);//true

Console.WriteLine(ex is A);//false
Console.WriteLine(ex as A != null);//false

class Something
{
  private readonly ID id;
  
  public Something()
  {
    id = ID.GetUniqueId();
    //INSERT INTO table (ID, State) VALUES ($id, 0)
  }

  private Something(ID id)
  {
    this.id = id;
  }
  
  public static IEnumerable<Something> GetAll()
  { 
     foreach(id in //SELECT ID FROM table)
       yield return new Something(id)
  }

  public int State
  {
    get { //SELECT State FROM table WHERE ID = $id }
    set { //UPDATE table SET State=$value WHERE ID = $id }
  }
}

internal interface IA
{
    int F();
}

class A : IA
{
    int IA.F()
    {
        return 1;
    }

    public int F()
    {
        return 2;
    }
}

A a1 = new A();
IA a2 = a1;

Console.WriteLine(object.ReferenceEquals(a1, a2));//true
Console.WriteLine(a1.F());
Console.WriteLine(a2.F());

object identity — identity is that property of an object that distinguishes each object from all others

A>>>dynamic a = new A {X = 42};
A>>>dynamic d = ExposedObject.From(a);
A>>>Console.WriteLine(d.X);//42
A>>>Console.WriteLine(object.ReferenceEquals(a, d));//false!!!
A>>>

A>Console.WriteLine(ex.Equals(o));//true
A>Console.WriteLine(object.ReferenceEquals(a, ex));//false!!!
A>

8.2.5.1 Identity

The identity operator is defined by the CTS as follows.
• If the values have different exact types, then they are not identical.
• Otherwise, if their exact type is a value type, then they are identical if and only if the bit
sequences of the values are the same, bit by bit.
• Otherwise, if their exact type is a reference type, then they are identical if and only if the
locations of the values are the same.

Identity is implemented on System.Object via the ReferenceEquals method.

8.2.5.2 Equality

For value types, the equality operator is part of the definition of the exact type. Definitions of equality should
obey the following rules:
• Equality should be an equivalence operator, as defined above.
• Identity should imply equality, as stated earlier.
• If either (or both) operand is a boxed value, equality should be computed by
o first unboxing any boxed operand(s), and then
o applying the usual rules for equality on the resulting values.

Equality is implemented on System.Object via the Equals method.

A>class Something
A>{
A>  private readonly ID id;
  
A>  public Something()
A>  {
A>    id = ID.GetUniqueId();
A>    //INSERT INTO table (ID, State) VALUES ($id, 0)
A>  }

A>  private Something(ID id)
A>  {
A>    this.id = id;
A>  }
  
A>  public static IEnumerable<Something> GetAll()
A>  { 
A>     foreach(id in //SELECT ID FROM table)
A>       yield return new Something(id)
A>  }

A>  public int State
A>  {
A>    get { //SELECT State FROM table WHERE ID = $id }
A>    set { //UPDATE table SET State=$value WHERE ID = $id }
A>  }
A>}
A>

A>Разжевать?

A>internal interface IA
A>{
A>    int F();
A>}

A>class A : IA
A>{
A>    int IA.F()
A>    {
A>        return 1;
A>    }

A>    public int F()
A>    {
A>        return 2;
A>    }
A>}

A>A a1 = new A();
A>IA a2 = a1;

A>Console.WriteLine(object.ReferenceEquals(a1, a2));//true
A>Console.WriteLine(a1.F());
A>Console.WriteLine(a2.F());
A>

A>Таки нашел

object identity — a characteristic of an object that provides a means to uniquely denote or refer to the object independent of its state or behavior