It's Actors All The Way Down

John Shutt has reformulated the foundations of LISP/Scheme [1]. Observing that Lambda is a primitive applicative constructor, he proposes Vau as a primitve operative constructor instead. This changes our focus from implicit evaluation to explicit evaluation. Applicatives evaluate their operands before evaluating the combination. Operatives act directly on their (unevaluated) operands, possibly evaluating them selectively. […]

This article is dedicated to the memory of John McCarthy (1927–2011) We are constantly on a quest for the elegant combination of simplicity and expressiveness in computer languages—what Alan Kay calls the “Maxwell’s Equations of Software“. An important early milestone was John McCarthy’s LISP [1] (The evolution of these ideas and the thinking behind them […]

In part 6 of our series implementing programming language constructs with actors, we explore meta-circular definition of imperative actor primitives. We have now moved beyond expressions which yield values, and focus on statements which cause effects. The constructs explored here are the heart of any actor-based system. In order to support actor primitive statements, our […]

In part 4 of our series implementing programming language constructs with actors, we extend our pattern matching behaviors to support pattern equations. These are true equations that express relationships between patterns. They form the basis for introducing LET and IF expressions. The grammar for our extended language is shown below. Changes from part 3 are […]

In part 3 of our series implementing programming language constructs with actors, we explore parallel evaluation of sub-expressions and introduce pairs. Pairs allow the construction of tuples, generalizing structured multi-part patterns and values. In order to support pair expressions and patterns, we’ve refactored the grammar from part 2 to separate out literal constants expressions and […]