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 […]

Mutable shared state is the root of all evil in concurrent systems. The history of concurrent computation is a basically the story of approaches to managing mutable shared state. The thread model, which has long held the dominant position, leads to intractable complexity [1]. The actor model captures state in the behavior of an actor. […]