[tombert]

Yeah, similarly, Joe Armstrong (RIP), co-creator of Erlang explained it to me like this:

> In distributed systems there is no real shared state (imagine one machine in the USA another in Sweden) where is the shared state? In the middle of the Atlantic? — shared state breaks laws of physics. State changes are propagated at the speed of light — we always know how things were at a remote site not how they are now. What we know is what they last told us. If you make a software abstraction that ignores this fact you’ll be in trouble.

He wrote this to me in 2014, and it has really informed how I think about these things.

[throwawaymaths]

The thing is that go channels themselves are shared state (if the owner closes the channel and a client tries to write you're not gonna have a good time)! Erlang message boxes are not.

[tombert]

Strictly speaking they’re shared state, but the way you model your application around channels is generally to have independent little chunks of work and the channels are just a means of communicating. I know it’s not one-for-one with Erlang.

[Kubuxu]

You can think of closing the channel as sending a message “there will be no further messages”, the panic on write is enforcement of that contract.

Additionally the safe way to use closing of a channel is the writer closing it. If you have multiple writers, you have to either synchronise them, or don’t close the channel.

[throwawaymaths]

Sure but the fact that it is shared state is why you can't naively have a go channel that spans a cluster but Erlang's "actor" system works just fine over a network and the safety systems (nodedowns, monitors etc) are a simple layer on top.

[kbolino]

You don't have to close a channel in Go and in many cases you actually shouldn't.

Even if you choose to close a channel because it's useful to you, it's not necessarily shared state. In a lot of cases, closing a channel behaves just like a message in its queue.

[aatd86]

Isn't entanglement in quantum physics the manifestation of shared state? tongue-in-cheek

[psychoslave]

Maybe. Or maybe we observe the same point of information source from two points which happen to be distant in the 3-coordinates we are accustomized to deal with, but both close to this single point in some other.

[aatd86]

but that still means that there is shared state on the projection from the higher tensor space.

orthogonality needs to be valid for all subspaces.