Auditors

The auditor subsystem allows objects to certify themselves as having certain properties. In order to gain certification, specimen objects must pass audition, a process in which the source code of the specimen object is revealed to an auditor, another object which examines the structure of the specimen and indicates whether it qualifies.

Stamps

Some auditors will admit any object which requests an audition. These auditors are called stamps. An object with a stamp is advertising behavior that is not necessarily reflected in the object’s structure. Stamps can be used to indicate that an object should be preferentially treated; additionally, a stamp with limited availability can be used to indicate that an object belongs to a privileged set of objects.

A Showing of Common Auditors

DeepFrozen

The DeepFrozen auditor proves that objects are immutable and that the objects they refer to are also DeepFrozen.

▲> DeepFrozen
DeepFrozen

Note

The specific property proven by DeepFrozen: For any DeepFrozen object, all bindings referenced by the object are also DeepFrozen.

Selfless

The Selfless auditor is a stamp. Any object bearing Selfless can also bear other stamps to indicate that equality comparisons with that object should be done in a customized way.

▲> Selfless
Selfless

Transparent

The Transparent auditor proves that an object implements a custom _uncall/0 Miranda method with certain properties. Any Transparent object can be compared by comparing the contents of its uncalled representation.

To prove an object Transparent, a small kit of facet objects must be obtained and attached to the maker definition:

def [makerAuditor :DeepFrozen, &&valueAuditor, &&serializer] := Transparent.makeAuditorKit()

Then the maker and object must both submit to audition. The maker must be DeepFrozen and the inner object Selfless:

def makeSwatch(color) as DeepFrozen implements makerAuditor:
    return object swatch implements Selfless, valueAuditor:
        to _uncall():
            return serializer(makeSwatch, [color])

The resulting maker will produce objects that can be compared as if by value:

▲> def red := makeSwatch("red")
▲> def xunre := makeSwatch("red")
▲> red == xunre
Result: true
▲> def blue := makeSwatch("blue")
▲> red == blue
Result: false

Note

Using the Transparent auditor as a guard is legal and works as expected, but is not required to obtain correct comparison behavior.

Note

Specifically, the property proven by Transparent is that uncalling the object is the inverse of calling the maker, and vice versa.

Bindings (WIP)

Todo

discuss bindings. Expand this section to “slots and bindings”? or discuss bindings under auditors?