crystal_packing 0.6.0

Core library for packing shapes in an infinite crystal lattice.
Documentation 
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//
// atom2.rs
// Copyright (C) 2019 Malcolm Ramsay <malramsay64@gmail.com>
// Distributed under terms of the MIT license.
//

use std::fmt;

use nalgebra::Point2;
use serde::{Deserialize, Serialize};

use crate::traits::Intersect;

#[derive(Clone, PartialEq, Debug, Serialize, Deserialize)]
pub struct Atom2 {
    pub position: Point2<f64>,
    pub radius: f64,
}

impl Intersect for Atom2 {
    fn intersects(&self, other: &Self) -> bool {
        let r_squared = (self.radius + other.radius).powi(2);
        // We have an intersection when the distance between the particles is less than the
        // combined radius of the two particles.
        (self.position - other.position).norm_squared() < r_squared
    }

    fn area(&self) -> f64 {
        std::f64::consts::PI * self.radius.powi(2)
    }
}

impl fmt::Display for Atom2 {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(
            f,
            "Atom2 {{ {}, {}, {} }}",
            self.position.x, self.position.y, self.radius
        )
    }
}

impl Atom2 {
    pub fn new(x: f64, y: f64, radius: f64) -> Self {
        Atom2 {
            position: Point2::new(x, y),
            radius,
        }
    }
}

#[cfg(test)]
mod test {
    use approx::assert_abs_diff_eq;

    use super::*;

    #[test]
    fn init_test() {
        let a = Atom2::new(0., 0., 1.);
        assert_abs_diff_eq!(a.position.x, 0.);
        assert_abs_diff_eq!(a.position.y, 0.);
        assert_abs_diff_eq!(a.radius, 1.);
    }

    #[test]
    fn distance_squared_test() {
        let a0 = Atom2::new(0., 0., 1.);
        let a1 = Atom2::new(0.5, 0., 1.);
        assert_abs_diff_eq!((a0.position - a1.position).norm_squared(), 0.25);
        assert!(a0.intersects(&a1));
    }

    #[test]
    fn intersection_test() {
        let a0 = Atom2::new(0., 0., 1.);
        let a1 = Atom2::new(1., 0., 1.);
        let a2 = Atom2::new(0.5, 0.5, 1.);
        let a3 = Atom2::new(1.5, 1.5, 1.);

        assert!(a0.intersects(&a1));
        assert!(a1.intersects(&a2));
        assert!(a3.intersects(&a2));

        assert!(!a0.intersects(&a3));
    }

    #[test]
    fn intersection_calculation_test() {
        let a0 = Atom2::new(0., 0., f64::sqrt(2.) / 2.);
        let a1 = Atom2::new(1., 1., f64::sqrt(2.) / 2.);
        let a2 = Atom2::new(1., 1., f64::sqrt(2.) / 2. - 2. * std::f64::EPSILON);
        println!("Radii: {}", a0.radius * a0.radius + a1.radius * a1.radius);
        assert!(a0.intersects(&a1));
        assert!(a1.intersects(&a2));

        assert!(!a0.intersects(&a2));
    }
}