Wyvern: A Simple, Typed, and Pure Object-Oriented Language

The simplest and purest practical object-oriented language designs
today are seen in dynamically-typed languages, such as Smalltalk
and Self. Static types, however, have potential benefits for productivity,
security, and reasoning about programs. In this paper, we describe
the design of Wyvern, a statically typed, pure object-oriented
language that attempts to retain much of the simplicity and expressiveness
of these iconic designs.
Our goals lead us to combine pure object-oriented and functional
abstractions in a simple, typed setting. We present a foundational
object-based language that we believe to be as close as
one can get to simple typed lambda calculus while keeping objectorientation.
We show how this foundational language can be translated
to the typed lambda calculus via standard encodings. We then
define a simple extension to this language that introduces classes
and show that classes are no more than sugar for the foundational
object-based language. Our future intention is to demonstrate that
modules and other object-oriented features can be added to our language
as not more than such syntactical extensions while keeping
the object-oriented core as pure as possible.
The design of Wyvern closely follows both historical and modern
ideas about the essence of object-orientation, suggesting a new
way to think about a minimal, practical, typed core language for
objects.