slop specification
This is the engineering specification for the MotionObservable operator: slop.
Overview
slop emits events in reaction to exiting and re-entering a slop region.
The slop region is centered around 0 and has a given size. This operator will not emit any
events until the upstream value exits this slop region, at which point onExit will be emitted. If
the upstream returns to the slop region then onReturn will be emitted.
Example usage
stream.slop(size: 50)
upstream size | downstream
20 50 |
10 50 |
60 50 | .onExit
70 50 |
10 50 | .onReturn
20 50 |
80 50 | .onExit
MVP
Expose a SlopEvent type
public enum SlopEvent {
case onExit
case onReturn
}
Expose a slop operator API
Accept a single argument defining the size of the slop region, centered around 0.
class MotionObservable<number> {
public func slop(size: number) -> MotionObservable<SlopEvent>
Calculate and emit the new slop event
class MotionObservable<number> {
func slop(size: number) -> MotionObservable<SlopEvent> {
return self
.thresholdRange(min: -size, max: size)
.rewrite([.whenBelow: .onExit, .whenWithin: .onReturn, .whenAbove: .onExit])
.dedupe()
.ignoreUntil(.onExit)