Overview

The h8io.stages.base package sits between the core abstractions and concrete stage implementations. The core Stage interface — implement apply and skip, supply an Evolution with evolve and dispose — is intentionally minimal. That minimalism is useful at the boundary, but it leaves every implementor to repeat the same structural boilerplate: a stage that never changes needs the same skip-returns-this pattern; a stage that wraps another needs to forward dispose; a stage backed by a pure function always writes the same Yield.Some(f(in), Status.Success, this).

The base package captures those patterns as composable, reusable traits. Concrete stages mix in what they need and implement only the logic that is genuinely specific to them.

The Immutability Hierarchy

The most common class of stages is those that do not change between runs: a filter, a transformer, a pure mapping. None of these need to carry state from one invocation to the next; their evolution always returns the same stage. The base package captures this with a small hierarchy, each layer sealing more boilerplate.