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    b = fx*GX + fy*GY;
    c = fx*fx + fy*fy - Q2;
    disc = b*b - A*c;               /* discriminant */
    x, y, z, delta;
    if (fabs(disc) < EPSILON) {
        z = b/A;
        x = (GX*z - fx)/Q;
        y = (fy - GY*z)/Q;
    } else {
        delta = sqrt(disc);
        z = (b + delta)/A;
        x = (GX*z - fx)/Q;
        y = (fy - GY*z)/Q;
        if (vhat * (PX*x + PY*y + PZ*z) < 0) {  /* wrong direction */
            z = (b - delta)/A;
            x = (GX*z - fx)/Q;
        y = (fy - GY*z)/Q;
        }
    }
    lat = asin(z);
    lat2 = lat*lat;
    earthlat = lat*(bi[0] + lat2*(bi[1] + lat2*(bi[2] + lat2*(bi[3] + \
               lat2*(bi[4] + lat2*(bi[5] + lat2*(bi[6])))))));
    earthlat = degrees(earthlat);

    /* Adjust longitude by 52 degrees */
    lon = degrees(atan2(x, y));
    earthlon = lon + 52.0;

    XPUSHs(sv_2mortal(newSVnv(earthlat)));
    XPUSHs(sv_2mortal(newSVnv(earthlon)));
    PUTBACK;
}


MODULE = Geo::Coordinates::VandH::XS    PACKAGE = Geo::Coordinates::VandH::XS

PROTOTYPES: DISABLE

double
radians (degrees)
    double    degrees

double
degrees (radians)
    double    radians

double
distance (v1, h1, v2, h2)
    double    v1
    double    h1
    double    v2
    double    h2

void
toVH (lat, lon)
    double    lat
    double    lon
    PREINIT:
    I32* temp;
    PPCODE:
    temp = PL_markstack_ptr++;
    toVH(lat, lon);
    if (PL_markstack_ptr != temp) {
      /* truly void, because dXSARGS not invoked */
      PL_markstack_ptr = temp;
      XSRETURN_EMPTY; /* return empty stack */
    }
    /* must have used dXSARGS; list context implied */
    return; /* assume stack size is correct */

void
toLatLon (v, h)
    double    v
    double    h
    PREINIT:
    I32* temp;
    PPCODE:
    temp = PL_markstack_ptr++;
    toLatLon(v, h);
    if (PL_markstack_ptr != temp) {
      /* truly void, because dXSARGS not invoked */
      PL_markstack_ptr = temp;
      XSRETURN_EMPTY; /* return empty stack */
    }
    /* must have used dXSARGS; list context implied */
    return; /* assume stack size is correct */