A good summary is available in Implementation Strategies for First-Class Continuations, an article by Clinger, Hartheimer, and Ost. I recommend looking at Chez Scheme’s implementation in particular. Stack copying isn’t that complex and there are a number of well-understood techniques available to improve performance. Using heap-allocated frames is also fairly simple, but you make a … Read more
It is concurrent, in the sense that many outstanding asychronous operations may be in progress at any time. It may or may not be multithreaded. By default, await will schedule the continuation back to the “current execution context”. The “current execution context” is defined as SynchronizationContext.Current if it is non-null, or TaskScheduler.Current if there’s no … Read more
(This is not yet an answer, but only some clues came up in my mind. I hope this will lead to the real answer, by myself or by someone else.) Call-by-Value is Dual to Call-by-Name — Philip Wadler In the above paper the author introduced the “Dual Calculus”, a typed calculus that is corresponding to … Read more
To compare it to C, the current continuation is like the current state of the stack. It has all the functions waiting for the result of the current function to finish so they can resume execution. The variable captured as the current continuation is used like a function, except that it takes the provided value … Read more
The first thing to realize about the continuation monad is that, fundamentally, it’s not really doing anything at all. It’s true! The basic idea of a continuation in general is that it represents the rest of a computation. Say we have an expression like this: foo (bar x y) z. Now, extract just the parenthesized … Read more
The general idea is correct – the remainder of the method is made into a continuation of sorts. The “fast path” blog post has details on how the async/await compiler transformation works. Differences, off the top of my head: The await keyword also makes use of a “scheduling context” concept. The scheduling context is SynchronizationContext.Current … Read more
My blog does explain what reset and shift do, so you may want to read that again. Another good source, which I also point in my blog, is the Wikipedia entry on continuation passing style. That one is, by far, the most clear on the subject, though it does not use Scala syntax, and the … Read more
I believe that continuations are a special case of callbacks. A function may callback any number of functions, any number of times. For example: var array = [1, 2, 3]; forEach(array, function (element, array, index) { array[index] = 2 * element; }); console.log(array); function forEach(array, callback) { var length = array.length; for (var i = … Read more
I’ll start with generators, seeing as they’re the simplest case. As @zvolkov mentioned, they’re functions/objects that can be repeatedly called without returning, but when called will return (yield) a value and then suspend their execution. When they’re called again, they will start up from where they last suspended execution and do their thing again. A … Read more