Function distance 

pub fn distance<A, B>(
    a: &A,
    b: &B,
) -> <DefaultDistanceStrategy<A, B> as DistanceStrategy<A, B>>::Out
where
    A: Geometry,
    B: Geometry,
    <<<A as Geometry>::Point as Point>::Cs as CoordinateSystem>::Family: DefaultDistance<<<<B as Geometry>::Point as Point>::Cs as CoordinateSystem>::Family>,
    DefaultDistanceStrategy<A, B>: DistanceStrategy<A, B> + Default,

Distance between two geometries using the default strategy for their coordinate-system pair.

Mirrors the no-strategy overload of boost::geometry::distance(g1, g2) from boost/geometry/algorithms/distance.hpp and the dispatch in boost/geometry/algorithms/detail/distance/interface.hpp. The default strategy is resolved via DefaultDistanceStrategy, which is the Rust analogue of Boost’s boost::geometry::strategy::distance::services::default_strategy<…>::type.