text: #define PJ_LIB__
  
  #include <errno.h>
  #include <math.h>
  
  #include "proj.h"
  #include "proj_internal.h"
  
  PROJ_HEAD(wink2, "Winkel II") "\n\tPCyl, Sph\n\tlat_1=";
  
  namespace { // anonymous namespace
  struct pj_opaque {
      double	cosphi1;
  };
  } // anonymous namespace
  
  #define MAX_ITER    10
  #define LOOP_TOL    1e-7
  
  
  static PJ_XY wink2_s_forward (PJ_LP lp, PJ *P) {           /* Spheroidal, forward */
      PJ_XY xy = {0.0, 0.0};
      int i;
  
      xy.y = lp.phi * M_TWO_D_PI;
      const double k = M_PI * sin (lp.phi);
      lp.phi *= 1.8;
      for (i = MAX_ITER; i ; --i) {
          const double V = (lp.phi + sin (lp.phi) - k) /
                              (1. + cos (lp.phi));
          lp.phi -= V;
          if (fabs (V) < LOOP_TOL)
                  break;
      }
      if (!i)
          lp.phi = (lp.phi < 0.) ? -M_HALFPI : M_HALFPI;
      else
          lp.phi *= 0.5;
      xy.x = 0.5 * lp.lam * (cos (lp.phi) + static_cast<struct pj_opaque*>(P->opaque)->cosphi1);
      xy.y = M_FORTPI * (sin (lp.phi) + xy.y);
      return xy;
  }
  
  static PJ_LP wink2_s_inverse(PJ_XY xy, PJ *P)
  {
      PJ_LP lpInit;
  
      lpInit.phi = xy.y;
      lpInit.lam = xy.x;
  
      return pj_generic_inverse_2d(xy, P, lpInit);
  }
  
  
  PJ *PROJECTION(wink2) {
      struct pj_opaque *Q = static_cast<struct pj_opaque*>(pj_calloc (1, sizeof (struct pj_opaque)));
      if (nullptr==Q)
          return pj_default_destructor(P, ENOMEM);
      P->opaque = Q;
  
      static_cast<struct pj_opaque*>(P->opaque)->cosphi1 = cos(pj_param(P->ctx, P->params, "rlat_1").f);
      P->es  = 0.;
      P->fwd = wink2_s_forward;
      P->inv = wink2_s_inverse;
  
      return P;
  }
  