Trait DefaultLength 

pub trait DefaultLength<Family> {
    type Strategy: Default;
}

“Which length strategy do we pick by default for this CS family?”

Mirrors v1’s DefaultDistance for the length algorithm — the Rust analogue of Boost’s services::default_strategy<Geometry, cs_tag> in strategies/length/services.hpp, specialised per CS in strategies/length/{cartesian,spherical,geographic}.hpp.

Length is unary, so — unlike DefaultDistance — there is exactly one family type parameter (there is no second geometry). Each family reports its default length strategy:

impl DefaultLength<CartesianFamily>  for CartesianFamily  { type Strategy = CartesianLength;  }
impl DefaultLength<SphericalFamily>  for SphericalFamily  { type Strategy = SphericalLength;  }
impl DefaultLength<GeographicFamily> for GeographicFamily { type Strategy = GeographicLength; }

The Strategy: Default bound matches Boost’s expectation that services::default_strategy<...>::type is default-constructible.

Required Associated Types

type Strategy: Default

The length strategy chosen for this family. Must implement Default because the free-function length(g) builds it without arguments.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl DefaultLength<CartesianFamily> for CartesianFamily

Cartesian family defaults to CartesianLength.

Mirrors the services::default_strategy<Geometry, cartesian_tag> specialisation in strategies/length/cartesian.hpp.

type Strategy = CartesianLength

impl DefaultLength<GeographicFamily> for GeographicFamily

Geographic family defaults to GeographicLength.

Mirrors the services::default_strategy<Geometry, geographic_tag> specialisation in strategies/length/geographic.hpp.

type Strategy = GeographicLength

impl DefaultLength<SphericalFamily> for SphericalFamily

Spherical family defaults to SphericalLength.

Mirrors the services::default_strategy<Geometry, spherical_tag> specialisation in strategies/length/spherical.hpp.

type Strategy = SphericalLength

Implementors