18,035 karma · joined March 2, 2015
Verifying my Blockstack ID is secured with the address 1L7ikyCFhG5zyVSosrQYDs2ZG4ikEFqgBQ https://explorer.blockstack.org/address/1L7ikyCFhG5zyVSosrQYDs2ZG4ikEFqgBQ
TLA+ is a specific kind of formal verification framework for software. The overall idea is that you can "prove" that some software works, rather than the typical "seems like it works" we aim for.
But under the covers, all formal verification schemes are (imho) best viewed as "very fancy testing". There are a few kinds of this fancy testing. TLA+ is the kind that can auto-generate all the relevant test cases for your code (there's more to it than that, but this definition works for now). So now instead of "I wrote a bunch of test cases, all that I could think of, and they pass" you have "I used TLA+ so I know I'm exercising all the possible test cases and they pass".
Here's the problem though: to achieve that trick, you have to write your code in a special language (TLA+). It isn't a tool that can be just pointed at regular production code.
So what you get to "prove" is a translation of your actual code into TLA+ code. It may be possible to auto-translate one to the other (I asked the original author if they did that, but no reply yet). Usually it's a manual process. Therefore you have "proof" but not quite as you know it, because you proved something different than what runs. But still more useful than a wet finger raised into the wind.
For this reason it's typically only used on narrow risky pieces of code (quorum voting is the canonical use case).
And speaking of "a less prosperous society" -- have you been to most of the USA recently? Doesn't look very prosperous to me vs most of Europe.
At first I thought the bell chime controller was a hobby project. Long ago there were many electronics firms in the Edinburgh area so someone who worked as an EE could easily have knocked up the controller using "appropriated" parts from work. But the soldering is not quite right. It's too good for a total beginner, but not good enough for a professional. Also the single chip I think implies an MCU of some sort, so it's not going to be more than about 30 years old. A date code from the chip would be nice.
Then I realized that "box to control church bells" is probably a thing and a quick Google search dragged up this: https://www.electronics-lab.com/project/church-bell-controll... note that the PCB in the 5th picture bears a more than passing resemblance to the one at Porty.
Fun fact: my Dad's mother's family ran a shop on the High Street in the late 1800's. The building is still there and is on the next block down the road from the police station.
And of course there are marker posts that say "buried fiber optic cable do not dig".