Enum DistanceConvention 

#[non_exhaustive]
pub enum DistanceConvention {
    ArcLength3d,
    PlanDistance,
    Unsupported,
}

The convention a station basis is measured in (#285): the curve-evaluation contract’s, re-exported so a caller can name it. Which distance a CurveEvaluator measures.

Naming this is not bureaucracy. For a Curve3::Elevated the plan distance and the true 3D arc length differ by sqrt(1 + grade^2), so a caller that assumes the wrong one misplaces a structure by 0.125 m per 100 m at a 5% grade and 0.5 m per 100 m at 10%. A silent mismatch is exactly the failure this contract exists to prevent, so the convention is part of the contract rather than provider trivia.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

ArcLength3d

True arc length along the 3D curve.

Distance d advances d metres along the curve as built.

PlanDistance

Distance along the horizontal projection.

This is how an alignment is authored: both the plan and the vertical profile are functions of plan distance, and a station written on a drawing is a plan distance. It is NOT the distance a wheel travels, which is longer by the grade factor.

Unsupported

This provider cannot recover a distance for this curve.

Reported rather than approximated: an ellipse needs elliptic integrals and a B-spline needs numeric inversion, and returning the native parameter as though it were a distance would be a lie a caller cannot detect.

Implementations

impl DistanceConvention

pub fn is_supported(self) -> bool

Whether a distance can be evaluated at all.

Trait Implementations

impl Clone for DistanceConvention

fn clone(&self) -> DistanceConvention

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for DistanceConvention

impl Debug for DistanceConvention

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

Formats the value using the given formatter.

impl Eq for DistanceConvention

impl Hash for DistanceConvention

fn hash<__H>(&self, state: &mut __H)

where __H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for DistanceConvention

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for DistanceConvention