[empthought]

Those aren't go routines, there's a yield sitting right there. And there's yield/return in your second example, and there's the equivalent in the promises example.

This isn't a terseness issue; it's an error issue. Favoring yield/return and equivalents over sequential code in CSP is exactly the same as favoring goto over while, or goto over exceptions. Necessary sometimes? Yes. Something to be celebrated and preferred? No.

The trouble is, of course, that in Javascript runtimes the "yield" or equivalent is how scheduling is achieved, because there is no capacity for preemption.

Thus, Node.js returns us to the bad old days of Windows 3.1 and System 6, where one faulty bit of code grinds the entire system to a halt.

Edit: Go goroutines of course also have a cooperative scheduler currently, but at least the result of having it isn't baked into the idioms and language constructs.

[spion]

True. Though I suppose that writing an async generator runner that utilizes multiple workers (e.g. via webworkers in browser, via isolates in node - if they ever happen) is also possibly doable at some time in the future. Those generators wont have any access to the current scope, but that might be better[1]

Still, scheduling would continue to be cooperative via yield (just split amongst multiple threads). Go is clearly much further ahead in that regard :D

[1]: https://groups.google.com/forum/#!topic/golang-nuts/hZjvk-EP...

note: I'm curious, doesn't shared state from those closures let you shoot yourself in the foot in Go? You still have to be careful not to use anything not thread-safe that can potentially change...

[empthought]

Sure, but you always opt-in to using variables that are scoped outside of the current thread. You don't opt-in to the explicit control operators encouraged by the style where you don't use sequential statements -- they are required in order to program correctly. This is why I think the goto analogy is appropriate.

[zsombor]

As of Go 1.2 (released a few weeks ago) goroutines are preempted. Sure currently this only happens in the presence of function calls, but it is hard to create a non preemptible infinite loop without function calls by accident.