EVOLUTION-MANAGER

Edit File: PJ_nell_h.c

#define PJ_LIB__ #include <math.h> #include "projects.h" PROJ_HEAD(nell_h, "Nell-Hammer") "\n\tPCyl., Sph."; #define NITER 9 #define EPS 1e-7 static XY s_forward (LP lp, PJ *P) { /* Spheroidal, forward */ XY xy = {0.0,0.0}; (void) P; xy.x = 0.5 * lp.lam * (1. + cos(lp.phi)); xy.y = 2.0 * (lp.phi - tan(0.5 *lp.phi)); return xy; } static LP s_inverse (XY xy, PJ *P) { /* Spheroidal, inverse */ LP lp = {0.0,0.0}; double V, c, p; int i; (void) P; p = 0.5 * xy.y; for (i = NITER; i ; --i) { c = cos(0.5 * lp.phi); lp.phi -= V = (lp.phi - tan(lp.phi/2) - p)/(1. - 0.5/(c*c)); if (fabs(V) < EPS) break; } if (!i) { lp.phi = p < 0. ? -M_HALFPI : M_HALFPI; lp.lam = 2. * xy.x; } else lp.lam = 2. * xy.x / (1. + cos(lp.phi)); return lp; } PJ *PROJECTION(nell_h) { P->es = 0.; P->inv = s_inverse; P->fwd = s_forward; return P; }