v0.6..1 - 25/04/2026

[0.6.1] - 2026-04-25

Fixed

• qtty-ffi packaged builds no longer depend on sibling workspace paths during
  build.rs; cargo package/cargo publish now verify cleanly from the
  packaged crate source.

• Updated crate docs, README dependency snippets, and the FFI version helper to
  the 0.6.1 release line (qtty_ffi_version() == 601).

[0.6.0] - 2026-04-25

Added

• Quantity-level real-number rounding helpers (qtty-core, re-exported by
  qtty) — Quantity<U, S> for S: Real now exposes floor(), ceil(),
  round(), trunc(), and fract(), matching the scalar Real surface while
  preserving unit types through common rounding workflows.

• assert_units_are_builtin! (qtty-core, #[doc(hidden)]) — compile-time
  assertion macro driven by each dimension's inventory macro under #[cfg(test)].
  Uses a supertrait bound pattern: adding a unit to a dimension inventory without
  also registering it in register_builtin_units! becomes a compile error. Catches
  the most common drift case (new unit added to the dimension file but the
  cross-dimension registry not updated).

• Facade consistency test (qtty/tests/inventory_consistency.rs) — compile-time
  integration test that uses exported inventory macros to assert every always-available
  unit in angular, length, time, mass, power, area, and volume
  is both re-exported in qtty::unit::* and has a root quantity alias in qtty::*.
  Adding a unit to an inventory but forgetting the corresponding lib.rs re-export
  or root alias generation now fails CI instead of silently becoming a missing export.

• New public acceleration / force / energy unit families across qtty-core
  and qtty, including Accel<L, T>, MeterPerSecondSquared,
  StandardGravity, SI newton/joule ladders, and feature-gated
  PoundForce, Dyne, Calorie, and electron-volt units.

• SquareOf<L> / CubeOf<L> helper aliases — new typed composition helpers
  for area and volume quantities derived from multiplied length quantities.

• New stable unit arithmetic layer (unit_arithmetic module) with UnitDiv and UnitMul extension traits that control output types for quantity division and multiplication, replacing the previous blanket impls.

• Generic recovery impls: U / U → Unitless, N / Per<N, D> → D, Per<N, D> * D → N, D * Per<N, D> → N.

• Macro-generated fallback pair tables for all built-in unit marker types: cross-unit division produces Per<A, B>, multiplication produces Prod<A, B>.

• Exported macros impl_unit_division_pairs!, impl_unit_multiplication_pairs!, and impl_unit_arithmetic_pairs! for downstream custom units to opt into the same generated arithmetic.

• asin, acos, and atan methods on Quantity<Unitless, S> (moved from Quantity<Per<U, U>>) so same-unit ratios keep ergonomic trig behavior.

• Comprehensive compile-time and runtime tests for unit arithmetic covering all recovery patterns, cross-unit pairs, and custom-unit registration.

• Added invalid-unit regression coverage for qtty-ffi quantity carriers so raw u32 unit IDs from C callers are rejected cleanly instead of producing undefined behavior.

• Added serde round-trip coverage for the Rust-side qtty-ffi carrier structs using their raw numeric unit IDs.

• qtty-ffi Area & Volume FFI coverage — DimensionId::Area (6) and DimensionId::Volume (7) are now part of the ABI, exposing 11 area units (SquareMeter … SquareDecimeter) and 13 volume units (CubicMeter … UsTeaspoon) with stable discriminant ranges 60000–60010 and 70000–70012 respectively.

• qtty-ffi discriminants.csv — new file that is the sole source of ABI-stable discriminant values. All unit metadata (ratios, symbols) is now derived at compile time from <Type as qtty::Unit>::RATIO/::SYMBOL, eliminating the historic dual-source-of-truth between units.csv and qtty-core.

• qtty crate-root module re-exports — qtty::{area, volume, acceleration, force, energy} are now re-exported at the crate root, and root quantity aliases are generated from the inventory macros for all built-in scalar families.

• Auto-generated FFI unit constants — qtty-ffi now emits named QTTY_UNIT_*
  constants from discriminants.csv for the full registry instead of maintaining
  a hand-written subset.

• AngularRate<N, D> type alias and AngularRateUnit trait as the primary
  names for angular-rate quantities (Angular / Time), replacing the
  misleading Frequency / FrequencyUnit names. The dimension alias is now
  AngularRate.

• Exact::checked_from_f64(value: f64) -> Option<Self> for converting a
  floating-point value to an exact scalar without silent overflow; returns
  None when the value is out of range or non-representable. (QTTY-003)

• Quantity::checked_to_lossy<T>() -> Option<Quantity<T, S>> for safe
  cross-unit conversion when the scalar type is Exact; returns None
  instead of silently saturating.

• 18 regression tests in qtty-core/tests/audit_regressions.rs covering
  cross-unit comparison symmetry, integer abs() boundary behaviour, and
  lossy/checked conversion semantics.

• MulAssign<S> for Quantity<U, S> — in-place scalar multiplication
  (q *= 2.0), symmetric with the pre-existing DivAssign<S>.

• Rem<Quantity<U, S>> for same-unit remainder — 5 m % 3 m == 2 m,
  complementing the pre-existing scalar Rem<S>.

• DAYS_PER_GREGORIAN_YEAR named constant (qtty-core::time) — replaces
  the four repeated 365.242_5 literals in Year/Decade/Century/Millennium
  ratio expressions.

Removed

• qtty-ffi units.csv — hardcoded ratio/symbol data removed; metadata is now derived from qtty-core trait constants so divergence is impossible at compile time.
• qtty-ffi deprecated helper functions — meters_into_ffi, try_into_meters, kilometers_into_ffi, try_into_kilometers, seconds_into_ffi, try_into_seconds, minutes_into_ffi, try_into_minutes, hours_into_ffi, try_into_hours, days_into_ffi, try_into_days, radians_into_ffi, try_into_radians, degrees_into_ffi, try_into_degrees have been removed. Use From/TryFrom directly (qty.into(), qty.try_into()).
• Removed the scalar-decimal feature and rust_decimal scalar support from qtty-core and the qtty facade crate.
• Breaking: Removed the public Simplify trait and .simplify() method from qtty-core and the qtty facade crate; unit arithmetic now resolves these cases at compile time.
• Breaking: Removed the deprecated frequency alias modules from qtty-core and qtty. Use angular_rate for Angular / Time quantities.
• Breaking: Removed deprecated Quantity<Unitless>::asin(), acos(), and atan() scalar-returning methods. Use asin_angle(), acos_angle(), and atan_angle() instead.

Changed

• Downstream crates can now keep more rounding and timestamp-normalization logic
  in typed quantities instead of erasing units to raw floating-point values for
  floor/ceil/round/fractional extraction.

• CODATA 2018 → 2022 (fundamental-physics) — Updated Bohr radius,
  classical electron radius, and electron reduced Compton wavelength to the
  CODATA 2022 recommended values. Planck length and atomic mass unit are
  unchanged (identical in both adjustments). Affected constants and their
  tests updated accordingly.

• Internal: inventory macros are now the canonical unit lists — every
  always-available unit family in qtty-core (angular, length, time,
  mass, power, area, volume, acceleration, force, energy) and the
  relevant feature-gated subfamilies now expose a {family}_units!($cb:path)
  macro that drives conversions, cross-unit ops, facade alias generation,
  FFI registry generation, and builtin-unit checks. No public API change.

• Internal: nominal length units have full pairwise From conversions —
  length_nominal_units! now drives impl_unit_from_conversions! for all 8 nominal
  units (SolarRadius, SolarDiameter, EarthRadius, EarthEquatorialRadius,
  EarthPolarRadius, JupiterRadius, LunarRadius, LunarDistance). Previously
  only SolarRadius ↔ Kilometer was generated. The explicit cross-group pair is
  retained.

• Breaking: Metric area marker types SquareMeter, SquareKilometer,
  SquareCentimeter, and SquareMillimeter are now Prod<Length, Length>
  aliases. side * side can therefore be assigned directly to SquareMeters,
  but symbol behavior now follows Prod (Display renders m·m; there is no
  dedicated SquareMeter::SYMBOL value like m²).

• Breaking: Same-unit division (Meter / Meter) now directly returns Quantity<Unitless> instead of Quantity<Per<Meter, Meter>>. Code that type-annotated the result as Quantity<Per<U, U>> must be updated.

• qtty-ffi build pipeline — build.rs now resolves all unit metadata by extracting inventory types from qtty-core source files and emitting <Type as qtty::Unit>::RATIO / ::SYMBOL expressions directly. Hardcoded floats are gone; the generated registry is always in sync with qtty-core by construction.

• qtty-ffi consistency test — tests/csv_inventory_consistency.rs replaced by tests/consistency.rs. The new test uses only compile-time UnitId::$variant assertions (forward check) and a lightweight runtime smoke-test that verifies trait-derived metadata matches the registry. The KNOWN_RATIO_DIVERGENCES / KNOWN_SYMBOL_DIVERGENCES workaround lists are gone.

• Breaking: Per<N, D> * D and D * Per<N, D> now directly return the numerator quantity (e.g., Quantity<Meter>) instead of Quantity<Prod<Per<N, D>, D>>. The .to() call to recover the numerator is no longer needed.

• Breaking: N / Per<N, D> now directly returns the denominator quantity (e.g., Quantity<Second>) instead of Quantity<Per<N, Per<N, D>>>.

• Breaking: asin/acos/atan are now on Quantity<Unitless> instead of Quantity<Per<U, U>>. Since same-unit division now yields Unitless directly, this is transparent for (a / b).asin() patterns.

• qtty-ffi quantity carrier fields and C-facing unit parameters now use raw u32/uint32_t unit IDs, and qtty_ffi_version() now reports ABI version 600.

• Quantity::sqrt() was renamed to Quantity::scalar_sqrt() to make it explicit that the operation returns the underlying scalar rather than a quantity with the original unit type.

• Breaking: Dimension aliases VelocityDim and AngularRateDim are now
  Velocity and AngularRate. At the qtty crate root, Velocity and
  AngularRate now name dimensions; the quantity aliases remain under
  qtty::velocity::Velocity<L, T> and qtty::frequency::AngularRate<N, D>.

• Breaking: Frequency<N, D>, FrequencyUnit, and FrequencyDim are
  removed. Use AngularRate<N, D>, AngularRateUnit, and AngularRate.

• Canonical symbols were tightened for two built-in units: Turn now renders as
  tr and Century now renders as c.

• Cross-unit comparison (==, <, …) is now symmetric: both operands
  are independently scaled to the same reference unit before comparison,
  eliminating the previous asymmetry where a == b could differ from
  b == a after a floating-point round-trip.

Fixed

• Pound-force value corrected (qtty-core::force, feature customary) —
  PoundForce::RATIO was 4.448_222_615_260_5 (typo in digit 6) instead of the
  exact NIST SP 1247 value 4.448_221_615_260_5 N (= g₀ × 1 lb). The error
  was one part per million and affected all conversions involving PoundForce.
  The accompanying test and docstring were updated to match.

• Year/Decade/Century/Millennium docstrings (qtty-core::time) — doc
  comments incorrectly described the Year struct and its multiples as "mean
  tropical year". The ratio used (365.242 5 d = DAYS_PER_GREGORIAN_YEAR) is the
  Gregorian calendar mean year (365 + 97/400), not the astronomical mean
  tropical year (≈ 365.242 19 d, which differs by ~27 s/yr). Docstrings for
  Year, Decade, Century, and Millennium now correctly say "mean Gregorian
  year" and explain the distinction. A stale // (tropical year) test comment in
  angular_rate.rs was corrected to match.

• Removed unitless.rs tombstone file (qtty-core) — a file containing only
  a comment ("The Unitless type has been removed") was left dangling after the
  removal of the Unitless type in a prior release. It was never included in any
  mod declaration and served no purpose; deleted to avoid confusion.

• f32 to_const precision — ratio conversion for f32-backed quantities
  now performs the U::RATIO / T::RATIO division in f64 before casting to
  f32, matching the f64 code path and avoiding doubled rounding error from
  two independent as f32 casts.

• Cleaned up stale scalar-decimal cfg gates, tests, and documentation left behind by the Decimal removal so current builds no longer emit unexpected_cfgs warnings.

• Made Quantity::mean() overflow-safe for integer-backed quantities by avoiding addition before division.

• Made Degrees::from_dms() and HourAngles::from_hms() safe for i32::MIN inputs by avoiding signed integer negation before widening.

• Fixed qtty-core pure no_std test builds by gating std-dependent internal test modules behind the std feature.

• Fixed qtty pure no_std test/example target checks by gating std-only integration tests and the all_units example.

• Generalized generated pairwise unit From/Into conversions across Real scalar types so non-default scalar modules such as qtty::f32 get the same conversion ergonomics as the default f64 surface.

• Refreshed the workspace and crate READMEs to match the current public API and publishing layout, including the all_units example command and the qtty-ffi package README.

• Updated crate docs and README dependency snippets to the current 0.6.0 release line.

• Integer abs() no longer panics in debug builds on the minimum signed
  value (e.g. i32::MIN); it now uses saturating_abs(), returning
  i32::MAX. (QTTY-002)

• qtty-ffi formatting now clamps requested precision to 100 to avoid
  pathological allocations and returns QTTY_ERR_BUFFER_TOO_SMALL for
  zero-length output buffers instead of QTTY_ERR_NULL_OUT.

• to_lossy() documentation now explicitly describes truncation and
  saturation semantics for integer scalars and warns that the result may
  not equal the original value. (QTTY-003)

• Crate-level docs in qtty-core and qtty corrected: removed the claim
  that all quantities are "backed by an f64"; serde section now says "raw
  scalar value" instead of "raw f64 value".