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

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.
G>>>Для C# две строки с одинаковым содержимым.

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

G>8.2.5.1 Identity

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

G>Identity is implemented on System.Object via the ReferenceEquals 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>>

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

G>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

G>>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

A>bool IsIdentical(object o1, object o2)
A>{
A>  return false;
A>}
A>

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

G>interface INumebr
G>{
G>    bool IsRational { get ; }
G>}
G>

G>8.3 Locations
G>Values are stored in locations. A location can hold only one value at a time. All locations are typed. The type
G>of the location embodies the requirements that shall be met by values that are stored in the location.

A>>bool IsIdentical(object o1, object o2)
A>>{
A>>  return false;
A>>}
A>>

G>var a = new object();
G>var b = a;
G>var c = new object();
G>Debug.Assert(IsIdentical(a,b) != IsIdentical(a,c));
G>

G>>interface INumebr
G>>{
G>>    bool IsRational { get ; }
G>>}
G>>

A>>>bool IsIdentical(object o1, object o2)
A>>>{
A>>>  return false;
A>>>}
A>>>

G>>var a = new object();
G>>var b = a;
G>>var c = new object();
G>>Debug.Assert(IsIdentical(a,b) != IsIdentical(a,c));
G>>