Delay by One

1 Version

Delays a stream t by one tick: emits the previous-tick datum each tick, with a configured initial_value on the first tick. Type preserving, holding exactly one datum of state so live and delayed streams can be compared tick-to-tick.

How it fits

Typical backends

Rate-of-change on a counter by comparing live against delayed.

Hold-last fallback switching between live and held value.

Diff against the previous frame, packed and serialised.

Caveats

Hard constraintThe configured initial_value is itself of type t, so it fixes t to a concrete type that both the input and output ports must agree with.
State lifetimeHolds exactly one tick of memory; longer histories require chaining several instances. The stored datum carries across ticks indefinitely until the next tick replaces it.
Parameter interactionThe initial_value is emitted once on the first tick and never again, even after a runtime restart of the surrounding deployment.
I/O contractOutput cadence matches input one-to-one; it emits exactly one datum per input tick and stalls if the upstream stalls.

Versions

e0342828defaultlatestTransformation
10/12/2023