sofars 0.6.0

Pure Rust implementation of the IAU SOFA library
Documentation 
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use crate::consts::{D2PI, DAS2R, DJ00, DJC, DMAS2R, TURNAS};
use std::ops::Rem;

struct Coeff {
    nl: i32,
    nlp: i32,
    nf: i32,
    nd: i32,
    nom: i32, /* coefficients of l,l',F,D,Om */
    ps: f64,
    pst: f64,
    pc: f64, /* longitude sin, t*sin, cos coefficients */
    ec: f64,
    ect: f64,
    es: f64, /* obliquity cos, t*cos, sin coefficients */
}

impl Coeff {
    const fn new(
        nl: i32,
        nlp: i32,
        nf: i32,
        nd: i32,
        nom: i32,
        ps: f64,
        pst: f64,
        pc: f64,
        ec: f64,
        ect: f64,
        es: f64,
    ) -> Self {
        Coeff {
            nl,
            nlp,
            nf,
            nd,
            nom,
            ps,
            pst,
            pc,
            ec,
            ect,
            es,
        }
    }
}

const X: [Coeff; 77] = [
    /* 1-10 */
    Coeff::new(
        0,
        0,
        0,
        0,
        1,
        -172064161.0,
        -174666.0,
        33386.0,
        92052331.0,
        9086.0,
        15377.0,
    ),
    Coeff::new(
        0,
        0,
        2,
        -2,
        2,
        -13170906.0,
        -1675.0,
        -13696.0,
        5730336.0,
        -3015.0,
        -4587.0,
    ),
    Coeff::new(
        0, 0, 2, 0, 2, -2276413.0, -234.0, 2796.0, 978459.0, -485.0, 1374.0,
    ),
    Coeff::new(
        0, 0, 0, 0, 2, 2074554.0, 207.0, -698.0, -897492.0, 470.0, -291.0,
    ),
    Coeff::new(
        0, 1, 0, 0, 0, 1475877.0, -3633.0, 11817.0, 73871.0, -184.0, -1924.0,
    ),
    Coeff::new(
        0, 1, 2, -2, 2, -516821.0, 1226.0, -524.0, 224386.0, -677.0, -174.0,
    ),
    Coeff::new(1, 0, 0, 0, 0, 711159.0, 73.0, -872.0, -6750.0, 0.0, 358.0),
    Coeff::new(
        0, 0, 2, 0, 1, -387298.0, -367.0, 380.0, 200728.0, 18.0, 318.0,
    ),
    Coeff::new(
        1, 0, 2, 0, 2, -301461.0, -36.0, 816.0, 129025.0, -63.0, 367.0,
    ),
    Coeff::new(
        0, -1, 2, -2, 2, 215829.0, -494.0, 111.0, -95929.0, 299.0, 132.0,
    ),
    /* 11-20 */
    Coeff::new(0, 0, 2, -2, 1, 128227.0, 137.0, 181.0, -68982.0, -9.0, 39.0),
    Coeff::new(-1, 0, 2, 0, 2, 123457.0, 11.0, 19.0, -53311.0, 32.0, -4.0),
    Coeff::new(-1, 0, 0, 2, 0, 156994.0, 10.0, -168.0, -1235.0, 0.0, 82.0),
    Coeff::new(1, 0, 0, 0, 1, 63110.0, 63.0, 27.0, -33228.0, 0.0, -9.0),
    Coeff::new(-1, 0, 0, 0, 1, -57976.0, -63.0, -189.0, 31429.0, 0.0, -75.0),
    Coeff::new(-1, 0, 2, 2, 2, -59641.0, -11.0, 149.0, 25543.0, -11.0, 66.0),
    Coeff::new(1, 0, 2, 0, 1, -51613.0, -42.0, 129.0, 26366.0, 0.0, 78.0),
    Coeff::new(-2, 0, 2, 0, 1, 45893.0, 50.0, 31.0, -24236.0, -10.0, 20.0),
    Coeff::new(0, 0, 0, 2, 0, 63384.0, 11.0, -150.0, -1220.0, 0.0, 29.0),
    Coeff::new(0, 0, 2, 2, 2, -38571.0, -1.0, 158.0, 16452.0, -11.0, 68.0),
    /* 21-30 */
    Coeff::new(0, -2, 2, -2, 2, 32481.0, 0.0, 0.0, -13870.0, 0.0, 0.0),
    Coeff::new(-2, 0, 0, 2, 0, -47722.0, 0.0, -18.0, 477.0, 0.0, -25.0),
    Coeff::new(2, 0, 2, 0, 2, -31046.0, -1.0, 131.0, 13238.0, -11.0, 59.0),
    Coeff::new(1, 0, 2, -2, 2, 28593.0, 0.0, -1.0, -12338.0, 10.0, -3.0),
    Coeff::new(-1, 0, 2, 0, 1, 20441.0, 21.0, 10.0, -10758.0, 0.0, -3.0),
    Coeff::new(2, 0, 0, 0, 0, 29243.0, 0.0, -74.0, -609.0, 0.0, 13.0),
    Coeff::new(0, 0, 2, 0, 0, 25887.0, 0.0, -66.0, -550.0, 0.0, 11.0),
    Coeff::new(0, 1, 0, 0, 1, -14053.0, -25.0, 79.0, 8551.0, -2.0, -45.0),
    Coeff::new(-1, 0, 0, 2, 1, 15164.0, 10.0, 11.0, -8001.0, 0.0, -1.0),
    Coeff::new(0, 2, 2, -2, 2, -15794.0, 72.0, -16.0, 6850.0, -42.0, -5.0),
    /* 31-40 */
    Coeff::new(0, 0, -2, 2, 0, 21783.0, 0.0, 13.0, -167.0, 0.0, 13.0),
    Coeff::new(1, 0, 0, -2, 1, -12873.0, -10.0, -37.0, 6953.0, 0.0, -14.0),
    Coeff::new(0, -1, 0, 0, 1, -12654.0, 11.0, 63.0, 6415.0, 0.0, 26.0),
    Coeff::new(-1, 0, 2, 2, 1, -10204.0, 0.0, 25.0, 5222.0, 0.0, 15.0),
    Coeff::new(0, 2, 0, 0, 0, 16707.0, -85.0, -10.0, 168.0, -1.0, 10.0),
    Coeff::new(1, 0, 2, 2, 2, -7691.0, 0.0, 44.0, 3268.0, 0.0, 19.0),
    Coeff::new(-2, 0, 2, 0, 0, -11024.0, 0.0, -14.0, 104.0, 0.0, 2.0),
    Coeff::new(0, 1, 2, 0, 2, 7566.0, -21.0, -11.0, -3250.0, 0.0, -5.0),
    Coeff::new(0, 0, 2, 2, 1, -6637.0, -11.0, 25.0, 3353.0, 0.0, 14.0),
    Coeff::new(0, -1, 2, 0, 2, -7141.0, 21.0, 8.0, 3070.0, 0.0, 4.0),
    /* 41-50 */
    Coeff::new(0, 0, 0, 2, 1, -6302.0, -11.0, 2.0, 3272.0, 0.0, 4.0),
    Coeff::new(1, 0, 2, -2, 1, 5800.0, 10.0, 2.0, -3045.0, 0.0, -1.0),
    Coeff::new(2, 0, 2, -2, 2, 6443.0, 0.0, -7.0, -2768.0, 0.0, -4.0),
    Coeff::new(-2, 0, 0, 2, 1, -5774.0, -11.0, -15.0, 3041.0, 0.0, -5.0),
    Coeff::new(2, 0, 2, 0, 1, -5350.0, 0.0, 21.0, 2695.0, 0.0, 12.0),
    Coeff::new(0, -1, 2, -2, 1, -4752.0, -11.0, -3.0, 2719.0, 0.0, -3.0),
    Coeff::new(0, 0, 0, -2, 1, -4940.0, -11.0, -21.0, 2720.0, 0.0, -9.0),
    Coeff::new(-1, -1, 0, 2, 0, 7350.0, 0.0, -8.0, -51.0, 0.0, 4.0),
    Coeff::new(2, 0, 0, -2, 1, 4065.0, 0.0, 6.0, -2206.0, 0.0, 1.0),
    Coeff::new(1, 0, 0, 2, 0, 6579.0, 0.0, -24.0, -199.0, 0.0, 2.0),
    /* 51-60 */
    Coeff::new(0, 1, 2, -2, 1, 3579.0, 0.0, 5.0, -1900.0, 0.0, 1.0),
    Coeff::new(1, -1, 0, 0, 0, 4725.0, 0.0, -6.0, -41.0, 0.0, 3.0),
    Coeff::new(-2, 0, 2, 0, 2, -3075.0, 0.0, -2.0, 1313.0, 0.0, -1.0),
    Coeff::new(3, 0, 2, 0, 2, -2904.0, 0.0, 15.0, 1233.0, 0.0, 7.0),
    Coeff::new(0, -1, 0, 2, 0, 4348.0, 0.0, -10.0, -81.0, 0.0, 2.0),
    Coeff::new(1, -1, 2, 0, 2, -2878.0, 0.0, 8.0, 1232.0, 0.0, 4.0),
    Coeff::new(0, 0, 0, 1, 0, -4230.0, 0.0, 5.0, -20.0, 0.0, -2.0),
    Coeff::new(-1, -1, 2, 2, 2, -2819.0, 0.0, 7.0, 1207.0, 0.0, 3.0),
    Coeff::new(-1, 0, 2, 0, 0, -4056.0, 0.0, 5.0, 40.0, 0.0, -2.0),
    Coeff::new(0, -1, 2, 2, 2, -2647.0, 0.0, 11.0, 1129.0, 0.0, 5.0),
    /* 61-70 */
    Coeff::new(-2, 0, 0, 0, 1, -2294.0, 0.0, -10.0, 1266.0, 0.0, -4.0),
    Coeff::new(1, 1, 2, 0, 2, 2481.0, 0.0, -7.0, -1062.0, 0.0, -3.0),
    Coeff::new(2, 0, 0, 0, 1, 2179.0, 0.0, -2.0, -1129.0, 0.0, -2.0),
    Coeff::new(-1, 1, 0, 1, 0, 3276.0, 0.0, 1.0, -9.0, 0.0, 0.0),
    Coeff::new(1, 1, 0, 0, 0, -3389.0, 0.0, 5.0, 35.0, 0.0, -2.0),
    Coeff::new(1, 0, 2, 0, 0, 3339.0, 0.0, -13.0, -107.0, 0.0, 1.0),
    Coeff::new(-1, 0, 2, -2, 1, -1987.0, 0.0, -6.0, 1073.0, 0.0, -2.0),
    Coeff::new(1, 0, 0, 0, 2, -1981.0, 0.0, 0.0, 854.0, 0.0, 0.0),
    Coeff::new(-1, 0, 0, 1, 0, 4026.0, 0.0, -353.0, -553.0, 0.0, -139.0),
    Coeff::new(0, 0, 2, 1, 2, 1660.0, 0.0, -5.0, -710.0, 0.0, -2.0),
    /* 71-77 */
    Coeff::new(-1, 0, 2, 4, 2, -1521.0, 0.0, 9.0, 647.0, 0.0, 4.0),
    Coeff::new(-1, 1, 0, 1, 1, 1314.0, 0.0, 0.0, -700.0, 0.0, 0.0),
    Coeff::new(0, -2, 2, -2, 1, -1283.0, 0.0, 0.0, 672.0, 0.0, 0.0),
    Coeff::new(1, 0, 2, 2, 1, -1331.0, 0.0, 8.0, 663.0, 0.0, 4.0),
    Coeff::new(-2, 0, 2, 2, 2, 1383.0, 0.0, -2.0, -594.0, 0.0, -2.0),
    Coeff::new(-1, 0, 0, 0, 2, 1405.0, 0.0, 4.0, -610.0, 0.0, 2.0),
    Coeff::new(1, 1, 2, -2, 2, 1290.0, 0.0, 0.0, -556.0, 0.0, 0.0),
];

/// nutation, IAU 2000B
pub fn nut00b(date1: f64, date2: f64) -> (f64, f64) {
    /* Units of 0.1 microarcsecond to radians */
    const U2R: f64 = DAS2R / 1e7;

    /* ---------------------------------------- */
    /* Fixed offsets in lieu of planetary terms */
    /* ---------------------------------------- */

    const DPPLAN: f64 = -0.135 * DMAS2R;
    const DEPLAN: f64 = 0.388 * DMAS2R;

    /* Interval between fundamental epoch J2000.0 and given date (JC). */
    let t = ((date1 - DJ00) + date2) / DJC;

    /* --------------------*/
    /* LUNI-SOLAR NUTATION */
    /* --------------------*/

    /* Fundamental (Delaunay) arguments from Simon et al. (1994) */

    /* Mean anomaly of the Moon. */
    let el = (485868.249036 + (1717915923.2178) * t).rem(TURNAS) * DAS2R;

    /* Mean anomaly of the Sun. */
    let elp = (1287104.79305 + (129596581.0481) * t).rem(TURNAS) * DAS2R;

    /* Mean argument of the latitude of the Moon. */
    let f = (335779.526232 + (1739527262.8478) * t).rem(TURNAS) * DAS2R;

    /* Mean elongation of the Moon from the Sun. */
    let d = (1072260.70369 + (1602961601.2090) * t).rem(TURNAS) * DAS2R;

    /* Mean longitude of the ascending node of the Moon. */
    let om = (450160.398036 + (-6962890.5431) * t).rem(TURNAS) * DAS2R;

    /* Initialize the nutation values. */
    let mut dp = 0.0;
    let mut de = 0.0;

    /* Summation of luni-solar nutation series (smallest terms first). */
    for i in (0..X.len()).rev() {
        /* Argument and functions. */
        let arg = (X[i].nl as f64 * el
            + X[i].nlp as f64 * elp
            + X[i].nf as f64 * f
            + X[i].nd as f64 * d
            + X[i].nom as f64 * om)
            .rem(D2PI);
        let sarg = arg.sin();
        let carg = arg.cos();

        /* Term. */
        dp += (X[i].ps + X[i].pst * t) * sarg + X[i].pc * carg;
        de += (X[i].ec + X[i].ect * t) * carg + X[i].es * sarg;
    }

    /* Convert from 0.1 microarcsec units to radians. */
    let dpsils = dp * U2R;
    let depsls = de * U2R;

    /* ------------------------------*/
    /* IN LIEU OF PLANETARY NUTATION */
    /* ------------------------------*/

    /* Fixed offset to correct for missing terms in truncated series. */
    let dpsipl = DPPLAN;
    let depspl = DEPLAN;

    /* --------*/
    /* RESULTS */
    /* --------*/

    /* Add luni-solar and planetary components. */
    let dpsi = dpsils + dpsipl;
    let deps = depsls + depspl;

    (dpsi, deps)
}