> Sadly another language with concurrency support that fails to learn the lessons from occam.

Weren't the top two lessons learned from occam about indeterminacy?:

1. If you ignore indeterminacy, you haven't really tackled concurrency, so you become irrelevant. CSP 1 ignored it, so occam 1 and 2 were designed to ignore it. While they became irrelevant for several reasons, I've long thought it was the fatal mistake of ignoring indeterminacy that made the demise of the original occam series inevitable.

2. If you tackle indeterminacy, but not its deeper consequences, you remain irrelevant. occam-π, which has added indeterminacy constructs as an after thought, has the problem that it's tackled it from the outside in.

During the 2019 concurrency talk panel that brought together three concurrency giants -- the late Joe Armstrong (Erlang), Sir Tony Hoare (CSP / occam), and the late Carl Hewitt (Actor Model) -- Tony said:

> The test for capturing the essence of concurrency is that you can use the same language for design of hardware and software, because the interface between those will become fluid. We've got to have a hierarchical design philosophy in which you can program each individual ten nanoseconds at the same time as you program over a 10 year time. And sequentiality and concurrency enter in to both those scales. So bridging the scale of granularity and of time and space is what every application has to do. The language can help them do that and that's a real criterion to designing the language.

Both Joe and Carl instantly agreed about what Tony said but also instantly disagreed about the central role of indeterminacy, and one could be forgiven for thinking Tony still hasn't learned the lesson of the mistake he made with CSP 1 and occam 1.

Erlang's "let it crash" concept distilled Joe's fundamental understanding of the nature of the physical universe, and how to write correct code given the inescapable uncertainty principle aka inescapable indeterminacy.

The Actor Model, which is a simple, purely mathematical model of purely physical computation, ironically the right theoretical grounding if you apply "Occam's Razor" to concurrent computation in our physical universe, contrasts sharply with the more "airy fairy" process calculi, which abstract processes as if one can truly ignore that, for such calculi to be useful in reality, the processes they describe must occur in reality -- and then indeterminacy becomes the key characteristic to confront, not an afterthought.

At least, that's my understanding.

I recall loving occam when I first read about it in the mid 1980s, partly because I was writing BCPL for a living at the time, and occam's syntax was based on BCPLs, but also because I was getting interested in concurrency, and fell in love with the Transputer, which was created by Inmos, a Bristol UK outfit, and I lived in the UK having spent a couple years living a few miles from Bristol.

But one can't deny reality, and the laws of physics, and the growing complexity of software, and the consequences of those two fundamentals, so eventually I concluded the Actor Model was going to outlive CSP and occam. I still think that, but am ever open to being persuaded of the error of my ways of thinking...