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A Two-Page Introduction to the Strongtalk Type System

David Griswold

First of all, a clarification: the name Strongtalk, originally used in an OOPSLA paper in 1993, referred just to the type system, which was originally grafted onto what was then ParcPlace Smalltalk. The name was later adopted for a far larger system, which includes the optimizing virtual machine, new "Blue Book" libraries that have been completely reimplemented to accomodate a number of goals in addition to type-safety, a new user interface framework, and a programming environment, as well as a second-generation implementation of the type system. The two are distinguished by referring either to the Strongtalk "system", or the Strongtalk "type system".

You will see a lot of type annotations as you browse around the system. A complete introduction to the type system is far beyond the scope of this tour. Right now, I will give you a crude two-page summary of the type system. Don't get intimidated; just read it and the simple examples should make the basic ideas clear. Once you've finished these two pages, you can read just about any type annotation in the system and get the basic idea (A copy of a somewhat more detailed workshop presentation by Gilad on the type system is here). There should be some more formal documentation on the type system soon.

The main ideas to keep in mind are:

Type System Intro (cont.) ==>