A key by which a Node’s additional information can be accessed.

  • Key
    • Basic
      • Identifiable
      • Object
        • Anything
Initializer
Key(String name)
Parameters:
  • name

    The name of this key. To avoid collisions with other keys, some use-site ID should be included, e. g. the name of the module that uses this key.

Attributes
hashshared actual Integer hash

The hash value of the value, which allows the value to be an element of a hash-based set or key of a hash-based map. Implementations must respect the constraint that:

  • if x==y then x.hash==y.hash.

Therefore, a class which refines equals must also refine hash.

In general, hash values vary between platforms and between executions of the same program.

Note that when executing on a Java Virtual Machine, the 64-bit Integer value returned by an implementation of hash is truncated to a 32-bit integer value by taking the exclusive disjunction of the 32 lowest-order bits with the 32 highest-order bits, before returning the value to the caller.

Refines Identifiable.hash ultimately refines Object.hash
idshared String idid = "`` `Type`.string ``:::``name

A unique ID of this key, composed of the name argument and the Type type argument.

stringshared actual String string

A developer-friendly string representing the instance. Concatenates the name of the concrete class of the instance with the hash of the instance. Subclasses are encouraged to refine this implementation to produce a more meaningful representation.

Refines Object.string
Inherited Attributes
Attributes inherited from: Object
hash, string
Methods
equalsshared actual Boolean equals(Object that)

Determine if two values are equal.

For any two non-null objects x and y, x.equals(y) may be written as:

x == y 

Implementations should respect the constraints that:

  • if x===y then x==y (reflexivity),
  • if x==y then y==x (symmetry),
  • if x==y and y==z then x==z (transitivity).

Furthermore it is recommended that implementations ensure that if x==y then x and y have the same concrete class.

A class which explicitly refines equals() is said to support value equality, and the equality operator == is considered much more meaningful for such classes than for a class which simply inherits the default implementation of identity equality from Identifiable.

Note that an implementation of equals() that always returns false does satisfy the constraints given above. Therefore, in very rare cases where there is no reasonable definition of value equality for a class, for example, function references (Callable), it is acceptable for equals() to be defined to return false for every argument.

Refines Identifiable.equals ultimately refines Object.equals
Inherited Methods
Methods inherited from: Object
equals