Perl 6 and Parrot Essentials, 2nd Edition

Objects

Perl 5, Perl 6, Python, and Ruby are all OO languages in some form or other, so Parrot has to have core support for objects and classes. Unfortunately, all these languages have somewhat different object systems, which made the design of Parrot’s object system somewhat tricky.^[26] It turns out that if you draw the abstraction lines in the right places, support for the different systems is easily possible. This is especially true if you provide core support for things like method dispatch, which the different object systems can use and override.

Generic Object Interfacing

Parrot’s object system is very simple—in fact, a PMC only has to handle method calls to be considered an object. Just handling methods covers well over 90% of the object functionality that most programs use, since the vast majority of object access is via method calls. This means user code that does the following:

object = some_constructor(1, 2, "foo");  
object.bar(12);

will work just fine, no matter what language the class that backs DEFANGED_object is written in, if DEFANGED_object even has a class backing it. It could be Perl 5, Perl 6, Python, Ruby, or even Java, C#, or Common Lisp; it doesn’t matter.

Objects may override other functionality as well. For example, Python objects use the basic PMC property mechanism to implement object attributes. Both Python and Perl 6 mandate that methods and properties share the same namespace, with methods overriding properties of the same name.

Parrot Objects

When we refer ...