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Patternia v0.8.0 Release Note

Release Date: February 27, 2026
Version: 0.8.0

Overview

Patternia v0.8.0 is an API and performance release.

Compared with v0.7.6, this version removes the legacy match(x, cases(...)).end() terminal form and focuses the public usage on match(x) | on{...}. It also upgrades variant dispatch internals with a tiered hot/warm/cold strategy for better large-branch behavior.

Highlights

API Update (Breaking)

  • Removed legacy terminal API:
  • match(x, cases(...)).end()
  • Recommended forms in v0.8.x:
  • match(x) | on{...};
  • match(x).when(...).when(...).end(); for chained style (deprecated; planned for future removal)
  • match(x).when(...).otherwise(...); for non-exhaustive matches (deprecated; planned for future removal)

Performance: Core Dispatch Algorithms in v0.8.0

  • Added explicit variant dispatch tiering:
  • hot_inline for small alternative counts
  • warm_segmented for medium alternative counts
  • cold_compact for large alternative counts
  • Added compact index mapping for large typed-variant dispatch:
  • active_index -> compact slot
  • miss goes directly to fallback path
  • hit jumps into dense trampoline table
  • Added typed-variant per-alt case-range narrowing:
  • only scans the relevant case range for the active alternative
  • Retained direct-reference bind fast path for variant typed bindings to reduce tuple plumbing on common paths.
  • Separated hot entry logic from cold large-branch logic using non-inline cold helpers to reduce hot-path code footprint.

Internal Architecture Cleanup

  • Further separated optimization metadata from runtime evaluation flow:
  • strategy/metadata stays in optimize.hpp
  • runtime execution stays in eval.hpp

Migration Guide

If you still use legacy terminal form, migrate to pipeline or chained API.

Before:

auto r = match(x, cases(
  lit(1) >> [] { return 1; },
  __ >> [] { return 0; }
)).end();

After:

auto r = match(x) | on{
  lit(1) >> [] { return 1; },
  __ >> [] { return 0; }
};

Compatibility Notes

  • API surface: breaking change in 0.8.0 due to removal of match(x, cases(...)).end().
  • Runtime semantics: unchanged for equivalent case ordering and fallback behavior.
  • Source compatibility: users of match(x) | on{...} and chain .when(...).end()/.otherwise(...) remain compatible.

Implementation Notes

  • include/ptn/core/common/optimize.hpp
  • Added dispatch tier model and variant metadata helpers.
  • include/ptn/core/common/eval.hpp
  • Integrated hot/warm/cold dispatch flow and cold-path helpers.
  • Updated typed/simple variant dispatch to use compact metadata.