Kenneth Iverson, inventor of APL, J, and winner of the 1979 Turing Award (his talk: “Notation as a Tool of Thought“), died last month at the age of 84. Although APL was quite popular, Iverson will be remembered as one who contributed more towards the formal unification of mathematical notation and computer science. This vein of programming has been less popular, particularly in the past twenty years and their emphasis on programming techniques that are “approachable” and business-oriented. The recent emphasis on heavily incremental, individually testable modules can, at it’s best, “feel“ somewhat like this style of programming, with a complete set of functions blossoming from seeds of composable thought. But Iverson insisted that “The utility of a language as a tool of thought increases with the range of topics it can treat, but decreases with the amount of vocabulary and the complexity of grammatical rules which the user must keep in mind,“ and would probably be offended at the suggestion that a C# or Java programmer using test-driven development was experiencing anything like APL or J.