(defun cons (x y) (lambda (z) (z x y))) (defun car (l) (l (lambda (x y) x))) (defun cdr (l) (l (lambda (x y) y)))
It's not like a lisp with 'just lambda' would be 'absurd and unusable'. I just showed you, we can implement cons, car, and cdr with just lambdas(hooray, closure! not clojure, closure...). Although there are some design decisions that had to be made, e.g. set, list.
Likewise "big" Church thesis programs exist and predate the oldest lambda calculus programs. They're even more unreadable (although everyone doing cs has at least looked at 2 of them).
Before that you will find more implicitly written programs that are definitely programs, in the sense that they are explicitly checked to be finite computation steps.
Even these informal algebraic programs not only predate LISP, Lambda and Church but a lot of them are rewrites of algorithms out of pure algebra that are definitely programs, just less formally written down.
You can trace the history of those back to the renaissance European city states (I refuse to accept al-Khawazarmi as having done anything but compile external sources).
And frankly, is there anyone here that has read Euclid's algorithm and doesn't think even the ancient Greek version is, when it comes right down to it, a valid computer program ? He didn't have the notion of generalized calculation (technically nobody did that correctly before Turing of course), but he had the notion of calculating various things by counting in specific ways. It's not that different, really. And it's only one of quite a set of programs written by Euclid of Alexandria.
Obviously Euclid's programs were never meant to be programs, but they are programs. They have a trivial mapping in pretty much any programming language that exists.
Oh, and Euclid uses recursion. Didn't define it, just uses it. Even Euclid very likely just compiled knowledge, didn't invent/discover it. Likely these algorithms were taught in Alexandria for at least a few decades before Euclid, so you could reasonably accurately say that there definitely were computer programmers in the 4th century BC, maybe even fifth.
And with the comment relating to "car" and "cdr", well, Euclid uses those functions. He doesn't define them beyond describing their effects, but he uses them. In that way, of course, he's acting like any other programmer. The only people defining car and cdr are developing the language, not any real programs.
