Struct Quantity 

pub struct Quantity { /* private fields */ }

An exact quantity: a magnitude in the SI base unit, tagged with its dimension.

Implementations

impl Quantity

pub fn of(value: Rational, unit: &Unit) -> Quantity

A quantity of value of unit — normalized to the SI base (value·scale + offset).

pub fn scalar(value: Rational) -> Quantity

A dimensionless quantity (a pure number) — for scaling.

pub fn si(magnitude: Rational, dimension: Dimension) -> Quantity

A quantity given directly by its SI-base magnitude and dimension — used for physical constants and any value whose dimension has no single named unit (e.g. the gas constant).

pub fn magnitude_si(&self) -> &Rational

The magnitude in the SI base unit.

pub fn dimension(&self) -> Dimension

pub fn in_unit(&self, unit: &Unit) -> Option<Rational>

The magnitude expressed IN unit — None if the dimensions differ (the forbidden cast). Linear: (si)/scale; affine: (si − offset)/scale. 1 mile in feet is exactly 5280.

pub fn add(&self, other: &Quantity) -> Option<Quantity>

self + other — None unless the dimensions match (you cannot add Length to Mass).

pub fn sub(&self, other: &Quantity) -> Option<Quantity>

self − other — None unless the dimensions match.

pub fn mul(&self, other: &Quantity) -> Quantity

self × other — magnitudes multiply, dimensions combine (Length × Length = Area).

pub fn div(&self, other: &Quantity) -> Option<Quantity>

self ÷ other — magnitudes divide, dimensions subtract. None on a zero divisor magnitude.

pub fn in_best_unit<'a>( &self, ladder: &'a [Unit], ) -> Option<(Rational, &'a Unit)>

Choose the most human-readable unit from ladder and return (magnitude_in_it, unit). The winner is the unit whose magnitude has the smallest absolute value that is still ≥ 1 (so 1500 m → (1.5, km), 0.5 km → (500, m)); if every candidate is below 1 the largest magnitude (closest to 1 from below) wins. Units of a different dimension are skipped, so a ladder with no same-dimension unit yields None. Exact — the conversion never rounds, and Quantity::of(mag, unit) reconstructs self. This is Design Law #3 (auto-scale to the most human unit), kept pure at the base layer so the interpreter Showable and AOT both reuse it.

Trait Implementations

impl Clone for Quantity

fn clone(&self) -> Quantity

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Quantity

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for Quantity

fn eq(&self, other: &Quantity) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Quantity

impl StructuralPartialEq for Quantity