rfa 0.5.9

A port ERFA to Rust.
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use crate::{rfam::{URSA_AULT, URSA_GRS80, URSA_WGS72, URSA_WGS84}, utils::*};
/*
**
**  Earth reference ellipsoids.
**
**  Given:
**     n    int         ellipsoid identifier (Note 1)
**
**  Returned:
**     a    double      equatorial radius (meters, Note 2)
**     f    double      flattening (Note 2)
**
**  Returned (function value):
**          int         status:  0 = OK
**                              -1 = illegal identifier (Note 3)
**
**  Notes:
**
**  1) The identifier n is a number that specifies the choice of
**     reference ellipsoid.  The following are supported:
**
**        n    ellipsoid
**
**        1     ERFA_WGS84
**        2     ERFA_GRS80
**        3     ERFA_WGS72
**
**     The n value has no significance outside the ERFA software.  For
**     convenience, symbols ERFA_WGS84 etc. are defined in erfam.h.
**
**  2) The ellipsoid parameters are returned in the form of equatorial
**     radius in meters (a) and flattening (f).  The latter is a number
**     around 0.00335, i.e. around 1/298.
**
**  3) For the case where an unsupported n value is supplied, zero a and
**     f are returned, as well as error status.
**
**  References:
**
**     Department of Defense World Geodetic System 1984, National
**     Imagery and Mapping Agency Technical Report 8350.2, Third
**     Edition, p3-2.
**
**     Moritz, H., Bull. Geodesique 66-2, 187 (1992).
**
**     The Department of Defense World Geodetic System 1972, World
**     Geodetic System Committee, May 1974.
**
**     Explanatory Supplement to the Astronomical Almanac,
**     P. Kenneth Seidelmann (ed), University Science Books (1992),
**     p220.
**
*/

pub fn eform(n: i8, a:&mut f64, f:&mut f64)->i32
{
    match n {
        URSA_WGS84 => {
            *a = 6378137.0;
            *f = 1.0 / 298.257223563;
        },
        URSA_GRS80 => {
            *a = 6378137.0;
            *f = 1.0 / 298.257222101;
        },
        URSA_WGS72 => {
            *a = 6378135.0;
            *f = 1.0 / 298.26;
        },
        _ => {
            /* Invalid identifier. */
            *a = 0.0;
            *f = 0.0;
            return -1;
        }
    }
    return 0;
}