Mia Golec, Emily Davis (both of CMU), and I have been spelunking in Simon and Newell's archives at CMU and came upon a remarkable complete listing of Simon's "heuristic coder" (https://dl.acm.org/doi/pdf/10.1145/321186.321192) [in the paper he calls it a "heuristic compiler", but the listing uses the term "coder"]. I've only just begun studying this fascinating find, which I intend to try to run on one of our IPL interpreters!