qtty

The user-facing crate that re-exports the qtty-core type system plus a curated set of astronomy-friendly units.

Highlights

• Strongly typed quantities backed by Quantity<U> to prevent mixing incompatible dimensions.
• Conversion is explicit and type-checked via to::<TargetUnit>() with zero runtime overhead.
• Includes handy derived aliases (velocity, frequency, …) and astronomy staples (AU, light-year, solar mass/luminosity).
• Works in no_std environments (uses libm) and has optional serde support.

Included units

Every unit module from qtty-core is re-exported at the crate root for convenience:

• Angular (Degrees, Radian, arcseconds, wrapping helpers)
• Time (Seconds, Minutes, Days, sidereal/astronomical variations)
• Length (Meters, Kilometers, AstronomicalUnit, LightYear, …)
• Mass (Kilograms, SolarMass)
• Power (Watts, SolarLuminosity)
• Velocity and frequency (Per<Length, Time>, Per<Angular, Time> aliases)
• unitless helpers for scalar quantities

Install

[dependencies]
qtty = "0.1.0"

Disable default features for no_std:

[dependencies]
qtty = { version = "0.1.0", default-features = false }

Quick start

use qtty::{Degrees, Radian};

let a = Degrees::new(90.0);
let r = a.to::<Radian>();
assert!((r.value() - core::f64::consts::FRAC_PI_2).abs() < 1e-12);

use qtty::{Kilometer, Kilometers, Second, Seconds};
use qtty::velocity::Velocity;

let d = Kilometers::new(1_000.0);
let t = Seconds::new(100.0);
let v: Velocity<Kilometer, Second> = d / t;
assert!((v.value() - 10.0).abs() < 1e-12);

Feature flags

• std (default): enables std support in qtty-core.
• serde: serializes/deserializes Quantity<U> as bare f64 values (unit is encoded by the type).
• pyo3: enables PyO3 conversions so Quantity<U> types convert to/from Python float and can be used directly as #[pyclass] fields (requires building with --features pyo3 for qtty-core).

Related crates

• qtty-core: the minimal zero-cost type system used underneath this facade.
• qtty-ffi: exposes the same quantities and conversions over a stable C ABI.

License

AGPL-3.0 (see ../LICENSE).