Thanks for sharing, I love these types of stories. Really makes me pine for the "old" days, and wonder if there's a parallel universe where technology took a very different route such that languages like APL, Lisp, and Smalltalk are used instead of JavaScript, Java, and C#, and what that world looks like.

> Some Lisp programmers had similar experiences, back in the day.

About 20 years ago (so not quite so far back) I was an engineering intern in an industry (nuclear energy) with two main tools: heavy number crunching software in Fortran, and Excel for everything else. The plant I was working at had just gotten some software for managing and tracking fuel movement (reactor cores are comprised of several hundred fuel bundles, which are re-arranged every 1-2 years), and my task was to set it up and migrate historical data from Excel spreadsheets, either by entering data manually with the GUI (which wasn't really that good) or using the primitive built-in import/export functions (CSV-based probably). Good intern task, right?

At some point I noticed this odd window running in the background whenever I started the program: "Gold Hill Common Lisp". Hm, what's this, it seems to have some kind of command line... and so I dived down the rabbit hole of the CL REPL and live image manipulation. I discovered the apropos command (or maybe GHCL had an actual UI for it?), which let me learn about all the internal data structures and methods, which I was able to use to quickly configure the plant specifics and import data.

"Oh, you're done already? OK next we need to get these custom reports out, talk to the vendor about implementing them. And see if you can now export data into our old report generator" (another spreadsheet of course). So I dutifully started the requisition process to get custom reports added, but while that was working through the system, I was stretching my new-found Lisp knowledge to not just dump out report data, but add the functionality to the UI. Coming from a background in C and Fortran I was fully ingrained with "write, compile, run" being how things worked. Image how much it blew my mind when I found out I could call a function in the REPL and actually add a menu to the running program!

One feature of the software was it could be used for "online" fuel movement tracking, which was traditionally done on paper, in duplicate. It's probably still done that way for good reasons, but still nice to have that electronic tracking. I was so proud when we were demonstrating it to the reactor operators, and they asked if we could add some little functionality (the details escape me), and I was able to say "yep no problem!" No requisitions, then back-and-forth with the vendor, eventually getting the feature in a year maybe. Really wish all software was so powerful (although admittedly my hijinks were a bit of a QA nightmare, but the software wasn't considered safety-related since there were many checks and paper records).

Fast-forward a couple years, after much coursework in Fortran and Matlab, I'm about to graduate and am now interviewing with the vendor. Question comes up "so what would you change about our software?" "Well, the interface is a bit clunky, I'd probably want to re-write it in a modern language like C++" :facepalm:.

Only years later, re-discovering CL, along with Racket and Clojure, did it occur to me how much was wrong with that response, and how sad that the key lesson of that semester internship had gone over my head.