rfa 0.5.9

A port ERFA to Rust.
Documentation 
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use crate::utils::*;
/*
**  - - - - - - - - - -
**   e r a G d 2 g c e
**  - - - - - - - - - -
**
**  Transform geodetic coordinates to geocentric for a reference
**  ellipsoid of specified form.
**
**  Given:
**     a       double     equatorial radius (Notes 1,4)
**     f       double     flattening (Notes 2,4)
**     elong   double     longitude (radians, east +ve)
**     phi     double     latitude (geodetic, radians, Note 4)
**     height  double     height above ellipsoid (geodetic, Notes 3,4)
**
**  Returned:
**     xyz     double[3]  geocentric vector (Note 3)
**
**  Returned (function value):
**             int        status:  0 = OK
**                                -1 = illegal case (Note 4)
**  Notes:
**
**  1) The equatorial radius, a, can be in any units, but meters is
**     the conventional choice.
**
**  2) The flattening, f, is (for the Earth) a value around 0.00335,
**     i.e. around 1/298.
**
**  3) The equatorial radius, a, and the height, height, must be
**     given in the same units, and determine the units of the
**     returned geocentric vector, xyz.
**
**  4) No validation is performed on individual arguments.  The error
**     status -1 protects against (unrealistic) cases that would lead
**     to arithmetic exceptions.  If an error occurs, xyz is unchanged.
**
**  5) The inverse transformation is performed in the function
**     eraGc2gde.
**
**  6) The transformation for a standard ellipsoid (such as ERFA_WGS84) can
**     more conveniently be performed by calling eraGd2gc,  which uses a
**     numerical code to identify the required a and f values.
**
**  References:
**
**     Green, R.M., Spherical Astronomy, Cambridge University Press,
**     (1985) Section 4.5, p96.
**
**     Explanatory Supplement to the Astronomical Almanac,
**     P. Kenneth Seidelmann (ed), University Science Books (1992),
**     Section 4.22, p202.
*/
pub fn gd2gce(a: f64, f: f64,
    elong: f64, phi: f64, height: f64, xyz: &mut[f64; 3])->i32
{

/* Functions of geodetic latitude. */
   let sp = sin(phi);
   let cp = cos(phi);
   let mut w = 1.0 - f;
   w = w * w;
   let d = cp*cp + w*sp*sp;
   if d <= 0.0 { return -1 };
   let ac = a / sqrt(d);
   let _as = w * ac;

/* Geocentric vector. */
   let r = (ac + height) * cp;
   xyz[0] = r * cos(elong);
   xyz[1] = r * sin(elong);
   xyz[2] = (_as + height) * sp;

/* Success. */
   return 0;

/* Finished. */

}