McCarthy published a paper in 1961 about if-then-else as a form of propositional logic replacing and/or/not, with its own identities playing a role like associa

McCarthy published a paper in 1961 about if-then-else as a form of propositional logic replacing and/or/not, with its own identities playing a role like associativity, de Morgan's laws, etc. This had to be invented. It's interesting to me that these identities and the canonical form McCarthy introduced there were exactly how BDDs work (when you just add memoizing, which was also invented about the same time) -- but BDDs weren't invented until the 1980s. (Explanation at https://codewords.recurse.com/issues/four/the-language-of-choice https://codewords.recurse.com/issues/four/the-language-of-ch...) It's easy to think things are obvious in hindsight.