That's the point of continuations, though. That's a feature, not a bug. When you create a continuation, you're saying "whatever happens after this, allow me to do it again at some later time." If the calling library happened to be in a loop, then the goal is to serialize that loop so that it can be invoked again, at a later point.

If you keep applying the continuation in a loop, then you'll get an infinite loop. But if you invoke the continuation once, (and if subsequent calls to fancylib_calculate() don't), then you'll get the ability to print

  val[0] = 42
  val[1] = 99
  ...
  val[9] = 7

In fact, you gain the ability to prevent the program from terminating, in a controlled fashion. Since you have access to the continuation, you can choose to invoke it on the 10th call to fancylib_calculate(), up to 3 times in a row. That would produce output like:

  val[0] = 42
  val[1] = 99
  ...
  val[9] = 7
  val[0] = 42
  val[1] = 99
  ...
  val[9] = 7
  val[0] = 42
  val[1] = 99
  ...
  val[9] = 7

Does that make sense? Apologies if we're talking past each other. I appreciate the patience.