We had a weird network issue in a production system, and because the interplay of different components was very difficult to debug I briefly investigated each component. This lead me to run Jersey (a JAX-RS implementation, ie. a REST library) with a debugger.
Jersey is written in a continuation passing style. That's the only time I've seen the style outside academic discussions of Scheme. I found the code flow difficult to grok and thought continuation passing didn't fit Java very well. That may all be just due to my lack of experience, though.
Granted, the alternatives to handling concurrency each have their own problems. Maybe this is a good idea; it will be interesting to see in practice.
Having native access to continuation control lets you avoid writing in continuation passing style. Itβs common to implement native continuation control with a compiler pass that automatically converts code into continuation passing style. (Similar to how you would transpile async/await in JavaScript.)
We're using the underlying continuations in Loom to build fibers. You don't need to pass continuations, you just write normal blocking code and the runtime takes care of yielding and scheduling. All you have to do is run things as fibers, which is pretty much like running them as threads.
I found iteratees to be the best of all worlds: you get the performance advantages of continuation-passing style, but you can still extract the start, middle, or end of a stream pipeline as an ordinary value that makes sense to reason about and test.
Jersey is written in a continuation passing style. That's the only time I've seen the style outside academic discussions of Scheme. I found the code flow difficult to grok and thought continuation passing didn't fit Java very well. That may all be just due to my lack of experience, though.
Granted, the alternatives to handling concurrency each have their own problems. Maybe this is a good idea; it will be interesting to see in practice.