> The underlying problem is that sequential languages do bad when you "bolt on" concurrency to them - unless said language is expressive enough to make it bearable
Really?
I'm not familiar with Erlang, but have you tried Go? Concurrency fits seamlessly into the language.
Go is not sequential, but concurrent. It has built-in primitives for handling concurrency, witness the `go` keyword. It also has special syntax for doing selective receive over channels, which in turn means that the concurrency of that language is definitely not "bolted on" in the sense I meant.
Perhaps you are confusing my definition of "sequential" with yours. I tend to use "sequential" as the opposite of "concurrent" like I have another, orthogonal, axis for "serial"/"parallel". So you can be serial/concurrent (Node.js is close to this. So is a 4.4BSD OS without any SMP support). And you can be sequential/parallel (GPUs is my preferred example).
Really?
I'm not familiar with Erlang, but have you tried Go? Concurrency fits seamlessly into the language.