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// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
part of dart.core;
/**
* The base class for all Dart objects.
*
* Because Object is the root of the Dart class hierarchy,
* every other Dart class is a subclass of Object.
*
* When you define a class, you should override [toString]
* to return a string describing an instance of that class.
* You might also need to define [hashCode] and [==], as described in the
* [Implementing map
* keys](https://www.dartlang.org/docs/dart-up-and-running/ch03.html#implementing-map-keys)
* section of the [library
* tour](http://www.dartlang.org/docs/dart-up-and-running/contents/ch03.html).
*/
class Object {
/**
* Creates a new [Object] instance.
*
* [Object] instances have no meaningful state, and are only useful
* through their identity. An [Object] instance is equal to itself
* only.
*/
const Object();
/**
* The equality operator.
*
* The default behavior for all [Object]s is to return true if and
* only if `this` and [other] are the same object.
*
* Override this method to specify a different equality relation on
* a class. The overriding method must still be an equivalence relation.
* That is, it must be:
*
* * Total: It must return a boolean for all arguments. It should never throw
* or return `null`.
*
* * Reflexive: For all objects `o`, `o == o` must be true.
*
* * Symmetric: For all objects `o1` and `o2`, `o1 == o2` and `o2 == o1` must
* either both be true, or both be false.
*
* * Transitive: For all objects `o1`, `o2`, and `o3`, if `o1 == o2` and
* `o2 == o3` are true, then `o1 == o3` must be true.
*
* The method should also be consistent over time,
* so whether two objects are equal should only change
* if at least one of the objects was modified.
*
* If a subclass overrides the equality operator it should override
* the [hashCode] method as well to maintain consistency.
*/
external bool operator ==(Object other);
/**
* The hash code for this object.
*
* A hash code is a single integer which represents the state of the object
* that affects [==] comparisons.
*
* All objects have hash codes.
* The default hash code represents only the identity of the object,
* the same way as the default [==] implementation only considers objects
* equal if they are identical (see [identityHashCode]).
*
* If [==] is overridden to use the object state instead,
* the hash code must also be changed to represent that state.
*
* Hash codes must be the same for objects that are equal to each other
* according to [==].
* The hash code of an object should only change if the object changes
* in a way that affects equality.
* There are no further requirements for the hash codes.
* They need not be consistent between executions of the same program
* and there are no distribution guarantees.
*
* Objects that are not equal are allowed to have the same hash code,
* it is even technically allowed that all instances have the same hash code,
* but if clashes happen too often, it may reduce the efficiency of hash-based
* data structures like [HashSet] or [HashMap].
*
* If a subclass overrides [hashCode], it should override the
* [==] operator as well to maintain consistency.
*/
external int get hashCode;
/**
* Returns a string representation of this object.
*/
external String toString();
/**
* Invoked when a non-existent method or property is accessed.
*
* Classes can override [noSuchMethod] to provide custom behavior.
*
* If a value is returned, it becomes the result of the original invocation.
*
* The default behavior is to throw a [NoSuchMethodError].
*/
external dynamic noSuchMethod(Invocation invocation);
/**
* A representation of the runtime type of the object.
*/
external Type get runtimeType;
}