Changelog

All notable changes to catena are documented here. The format follows Keep a Changelog; versions follow semantic versioning.

1.1.0 — 2026-08-31

The first usable release. v1.0.0 was published briefly and withdrawn; it is retracted in go.mod and should not be used. Start here.

The library

• Seq[T] — lazy iter.Seq[T] with 84 methods (37 chainable), built on Go 1.27 generic methods; range works directly and conversion to and from the standard iterator types is free.
• Try[T] — fallible sequences where the consumer chooses the error policy (Collect aborts, CollectAll gathers, Ignore skips), under five uniform rules for how errors flow through intermediates.
• Seq2[K, V] — the stdlib pair bridge; List[T] — the eager mirror, generated and conformance-checked to agree with AsSeq().
• The memory-class operators: FoldBy (grouped aggregation bounded by keys, not elements), TopNBy/BottomNBy (bounded stable heap), DedupeBy (O(1) streaming distinct), ChunkedBy, Windowed, JoinBy (relational inner join).
• Every operator’s contract — argument edges, memory class, drain class, ordering and tie policy, error semantics — specified in SPEC.md and enforced by the C1–C15 conformance suite, a completeness check that fails CI for any unregistered export, property tests, and 100% statement coverage of the library.
• An operator reference covering all 182 operators, each with a worked example that go test runs and whose output it verifies.
• examples/ — eight runnable programs, all executed in CI.
• Performance measured three ways (hand loop / raw iter.Seq closures / catena) with the standing rule that catena meets the raw mechanism wherever the two compile on equal terms — it wins on multi-stage pipelines and terminals, and trails by 4–13% on single-stage shapes, where the baseline inlines into its consumer and a library call cannot. Operators compose by direct source invocation rather than range, which makes a 4-stage pipeline 25% faster than the same pipeline hand-built from raw closures.