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use russell_lab::{Matrix, Vector};
/// Defines a line (segment) with 3 nodes (quadratic functions)
///
/// 
///
/// # Local IDs of nodes
///
/// ```text
/// 0-----------2-----------1 --> r
/// -1.0 0.0 1.0
/// ```
///
/// # Notes
///
/// * The reference coordinates range from -1 to +1 with the geometry centred @ 0
/// * This shape is a lower-order version of [super::Lin5]
/// * This shape is a higher-order version of [super::Lin2]
pub struct Lin3 {}
impl Lin3 {
pub const GEO_NDIM: usize = 1;
pub const NNODE: usize = 3;
pub const NEDGE: usize = 0;
pub const NFACE: usize = 0;
pub const EDGE_NNODE: usize = 0;
pub const FACE_NNODE: usize = 0;
pub const FACE_NEDGE: usize = 0;
pub const N_INTERIOR_NODE: usize = 1;
#[rustfmt::skip]
pub const NODE_REFERENCE_COORDS: [[f64; Lin3::GEO_NDIM]; Lin3::NNODE] = [
[-1.0],
[ 1.0],
[ 0.0],
];
pub const INTERIOR_NODES: [usize; Lin3::N_INTERIOR_NODE] = [2];
/// Computes the interpolation functions
///
/// # Output
///
/// * `interp` -- interpolation function evaluated at ksi (nnode)
///
/// # Input
///
/// * `ksi` -- reference coordinates with length ≥ geo_ndim
pub fn calc_interp(interp: &mut Vector, ksi: &[f64]) {
let r = ksi[0];
interp[0] = 0.5 * (r * r - r);
interp[1] = 0.5 * (r * r + r);
interp[2] = 1.0 - r * r;
}
/// Computes the derivatives of interpolation functions with respect to the reference coordinates
///
/// # Output
///
/// * `deriv` -- derivatives of the interpolation function with respect to
/// the reference coordinates ksi, evaluated at ksi (nnode,geo_ndim)
///
/// # Input
///
/// * `ksi` -- reference coordinates with length ≥ geo_ndim
pub fn calc_deriv(deriv: &mut Matrix, ksi: &[f64]) {
let r = ksi[0];
deriv.set(0, 0, r - 0.5);
deriv.set(1, 0, r + 0.5);
deriv.set(2, 0, -2.0 * r);
}
}