I wanted to tackle a rewrite of a legacy LISP program, used by AutoCAD, to take in a list of 3D coordinate points, and output a DWG of a 2D projection (from whi

I wanted to tackle a rewrite of a legacy LISP program, used by AutoCAD, to take in a list of 3D coordinate points, and output a DWG of a 2D projection (from which to create a jig on which to assemble a prototype). Cool stuff, right? My intent was to create a "proper" script in AutoCAD to actually create 3D objects from the input data, and let the program do the projection to a 2D drawing. (I'm still not sure if that would have been possible; I never got that far.) I had never written in LISP before, so I bought a book! I was having trouble reading the program on the computer, so I printed out the roughly 15,000 lines. Not a lot, I know, but it was about an inch and a half thick stack of paper. I started going through it. It consisted of LOTS of subroutines. Thousands. Each one neatly formed; no more than a couple hundred lines. It gave me hope. It read in the text file, created a blob of a string, and then passed that blob to the first subroutine. Then it passed to the next subroutine. And then the next, and so on. As far as I could tell, it never called a subroutine a second time, and it never returned to the starting method. Given the strangeness of LISP, I couldn't figure out what it was doing, or why. The guy who wrote it had retired, and we didn't get along anyway, so I didn't try to chase down what his thinking was. I gave up. To my knowledge, they're still using that program 17 years later.