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Level 4 is turing complete.

There's two parts that I was talking about. Things that are not quite that and the fact that configuration can have that capability in a fairly useless context.

When I'm dealing with personal things or stuff that few people use I will often make the configuration just something I eval/source.

So it in theory has the same functionality as the underlying programming language, but in practice you're just supposed to use it like an INI.

Here's a fairly large personal project where I use that

https://github.com/kristopolous/music-explorer

It actually allowed me to change the behavior on whether I'm running my program from my office or home. So invoking the full fidelity of the underlying language actually has its benefits at times.



Level 4 / total programming languages are not turing complete. Because you can't simulate every turing machine in them, only some subset that provably halts. (And because the halting problem is undecidable, there will always be some turing machines that actually do halt but still can't be simulated because the compiler can't prove it)


It's been edited since I wrote this and it's now 5 instead of 4

It didn't originally use the obscure formal idea of a "total" language


How is a total language obscure? It's a language describing total functions


oh I knew I was going to get this. Now I have to define obscure. Let's go!

Github has two (yes, just 2) repositories referring to them: (that's nearly 0.000 000 5% of Github I hear you say)

https://github.com/search?q=%22total%20language%22&type=repo...

But maybe that's unfair. Let's try a software engineering encyclopedia!

Ok, "Encyclopedia of Software Engineering (2011)" doesn't have it: https://archive.org/details/encyclopediaofso0001unse_m2w7/pa...

Alright what about programming language text book?

Well, "Programming language design concepts" (2004) also doesn't mention it https://archive.org/details/programminglangu0000watt/mode/2u...

What about Donald Knuth? Surely! Nope, not on the versions of his text on archive.org at least.

https://archive.org/details/artofcomputerpro0002knut_u2o0/mo... also https://archive.org/details/artofcomputerpro0000unse_e7w6/mo...

Oh let's go to arxiv. I'm sure of the ~400 CS papers that go up daily there'd be hundreds of ... oh wait, we got 5 spreading over 17 years: https://arxiv.org/search/?query=%22total+language%22&searcht... about 1 every 3 years. Alright.

And thus with 5 different sampling methods all supporting the same conclusion I will support the claim that it is obscure.

I know how on the internet, vibes tends to win over cited defensible evidence but I did it anyway. Maybe we can be all be adults some day.




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