Processes in and returns the Yield carrying the optional output, the status and the continuation.

A stage that throws from here must have released its own resources first — see the Lifecycle section above.

Composes this evolution with the one downstream of it, so that for every status

composed(s) == self(s) ~> that(s)

This is how Yield composition carries both continuations of a pipeline forward; application code rarely calls it directly.

Releases everything held by the Stage that produced this evolution. That stage is permanently unusable afterwards — neither applied nor skipped again — and this is the only place its resources are released.

Whoever terminates a pipeline is responsible for disposing the evolution of the final Yield, so that the continuation is released at once instead of being carried around. The reference terminal driver is the execute extension method of h8io.stages.base in the lib module.

dispose() stays valid after evolve has been called on the same instance, and must then release everything still alive, including whatever building the continuation acquired. evolve hands over no ownership: this evolution remains the cleanup point for its lineage until the continuation has run and produced an evolution of its own, which takes the role over from that moment.

Exceptions are not part of this contract: a stage whose apply throws produces no yield and therefore no evolution, so there is nothing to dispose — it must clean up after itself (see the Lifecycle section in Stage).

A no-op is a fine implementation for a stage holding nothing external.

The next stage, for the given status.

May release what belongs to this generation alone — anything the returned stage and its own evolution will not reuse.

evolve and dispose are not mutually exclusive. Usually only one of them is called on an instance: a terminal driver disposes, a continuing pipeline evolves and drops the previous evolution. But a caller may do both, and operators owning their inner stage (Loop, Repeat and the rest of h8io.stages.cycles in the lib module) do exactly that — they evolve eagerly and keep the inner dispose as the cleanup handle of the generation they just built.

The pure mapping function applied to each input value.

Applies f to every stage this evolution would return, leaving disposal delegated to it unchanged.

The way an operator keeps its wrapping in place across generations: the continuation comes back wrapped the same way the current stage is.

Returns this stage's Evolution without consuming an input.

Called instead of apply whenever the stage takes part in a run but has nothing to process: the upstream yielded no output, or a binary operator excluded this branch. The evolution must be the one the stage would have returned had it run. Like apply, skip() may perform side effects — a decorator, for instance, may advance or release the inner stage it owns.

Composes this stage with that, feeding this stage's output into it. See the Composition section above for what happens when there is no output to feed.