very low: stop as argument for loop and cycle

[betula]

loop(async (stop) => {
  const data = await action;
  if (stop.val) return;
  // ...
});

loop(function* (stop) {
  const data = yield action;
  // ...
});

cycle((stop) => {
  this.a = a.val;
});

You need to take this as a shortcut to the stoppable mechanism.

[betula]

The loop removed in 0.6.0
cycle with stop function as a first argument added to "the stream of conciseness 0.7+ roadmap"