#include <math.h>

#include "proj.h"

#include "proj_internal.h"

PROJ_HEAD(eck5, "Eckert V") "\n\tPCyl, Sph";

#define XF 0.44101277172455148219

#define RXF 2.26750802723822639137

#define YF 0.88202554344910296438

#define RYF 1.13375401361911319568

static PJ_XY eck5_s_forward(PJ_LP lp, PJ *P) { /* Spheroidal, forward */

    PJ_XY xy = {0.0, 0.0};

    (void)P;

    xy.x = XF * (1. + cos(lp.phi)) * lp.lam;

    xy.y = YF * lp.phi;

    return xy;

}

static PJ_LP eck5_s_inverse(PJ_XY xy, PJ *P) { /* Spheroidal, inverse */

    PJ_LP lp = {0.0, 0.0};

    (void)P;

    lp.phi = RYF * xy.y;

    lp.lam = RXF * xy.x / (1. + cos(lp.phi));

    return lp;

}

PJ *PJ_PROJECTION(eck5) {

    P->es = 0.0;

    P->inv = eck5_s_inverse;

    P->fwd = eck5_s_forward;

    return P;

}