use ndarray::{Array1, Array2, ArrayView1, ArrayView2, array};
use crate::geometry::manifold::{
GeometryResult, RiemannianManifold, check_len, identity, wrap_angle, zero_christoffel,
};
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct CircleManifold;
impl CircleManifold {
pub const fn new() -> Self {
Self
}
}
impl RiemannianManifold for CircleManifold {
fn dim(&self) -> usize {
1
}
fn tangent_basis(&self, point: ArrayView1<'_, f64>) -> GeometryResult<Array2<f64>> {
check_len("Circle point", point.len(), 1)?;
Ok(identity(1))
}
fn exp_map(
&self,
point: ArrayView1<'_, f64>,
tangent_vec: ArrayView1<'_, f64>,
) -> GeometryResult<Array1<f64>> {
check_len("Circle point", point.len(), 1)?;
check_len("Circle tangent", tangent_vec.len(), 1)?;
Ok(array![wrap_angle(point[0] + tangent_vec[0])])
}
fn log_map(
&self,
p_from: ArrayView1<'_, f64>,
p_to: ArrayView1<'_, f64>,
) -> GeometryResult<Array1<f64>> {
check_len("Circle source", p_from.len(), 1)?;
check_len("Circle target", p_to.len(), 1)?;
Ok(array![wrap_angle(p_to[0] - p_from[0])])
}
fn parallel_transport(
&self,
point_along: ArrayView2<'_, f64>,
vec: ArrayView1<'_, f64>,
) -> GeometryResult<Array1<f64>> {
if point_along.nrows() > 0 {
check_len("Circle path width", point_along.ncols(), 1)?;
}
check_len("Circle transported vector", vec.len(), 1)?;
Ok(vec.to_owned())
}
fn metric_tensor(&self, point: ArrayView1<'_, f64>) -> GeometryResult<Array2<f64>> {
check_len("Circle metric point", point.len(), 1)?;
Ok(identity(1))
}
fn christoffel_symbols(&self, point: ArrayView1<'_, f64>) -> GeometryResult<Vec<Array2<f64>>> {
check_len("Circle Christoffel point", point.len(), 1)?;
Ok(zero_christoffel(1))
}
fn sectional_curvature(
&self,
point: ArrayView1<'_, f64>,
tangent_pair: (ArrayView1<'_, f64>, ArrayView1<'_, f64>),
) -> GeometryResult<f64> {
check_len("Circle curvature point", point.len(), 1)?;
check_len("Circle curvature tangent u", tangent_pair.0.len(), 1)?;
check_len("Circle curvature tangent v", tangent_pair.1.len(), 1)?;
Ok(0.0)
}
}