For some reason this made me think about all of the potential complexities that can be involved in CLOS in calling a generic function and some method(s) actually being invoked...
I honestly thought of typing that one out here, lol.
You have the camera... I have the monitor... How about I flash QR codes? Oh, the camera is on top of the monitor, facing the room? Well, at night, I could FLASH the monitor full white in binary, and you can see the light on the chair and wall, right?
I'll leave the disc head on the sector number. You read the disc head position.
I'll exit my function on a time modulo a number to encode the remainder. You see what time you were called, and can decode the remainder.
I'll warm the CPU to a temperature... you read the temperature...
Global variable.
Parameter to a function.
Pass a functor/lambda, get the value.
Environment variable.
Registry.
File.
Store it in a ping response.
VRAM texture that you write and then read.
Database.
REST server.
I'm pretty sure I could come up with a thousand ways.
But... why? Why do I want to write this book? Why has it been on my mind?