Lambda the Ultimate

The When, Why and Why Not of the BETA Programming Language by Bent Bruun Kristensen, Ole Lehrmann Madsen, and Birger Møller-Pedersen from HOPL-III. BETA was an ambitious follow up to Simula - with orthogonality being a major design goal. The main things I found of interest are the attempts to create a unified abstraction pattern, the emphasis on modeling consistency between design and implementation, and the use of coroutines (ala Simula) for concurrency.

BETA is a programming language that has only one abstraction mechanism, the pattern, covering abstractions like record types, classes with methods, types with operations, methods, and functions. Specialization applies to patterns in general, thus providing a class/subclass mechanism for class patterns, a subtype mechanism for type patterns, and a specialization mechanism for methods and functions.

And while I'm at it, the original entry for HOPL-I on The Development of the SIMULA Languages by Kristen Nygaard and Ole-Johan Dahl is available (starts on page 3). SIMULA is one of a handful of most influential programming languages of all time. I found the following to be amusing:

In the spring of 1967 a new employee at the NCC in a very shocked voice told the switchboard operator: "Two men are fighting violently in front of the blackboard in the upstairs corridor. What shall we do?" The operator came out of her office, listened for a few seconds and then said: "Relax, it's only Dahl and Nygaard discussing SIMULA".

(Link to previous HOPL-III papers on LtU).