text: #define PROJ_PARMS__ \
  	double ml0; \
  	double *en;
  #define PJ_LIB__
  #include <projects.h>
  PROJ_HEAD(poly, "Polyconic (American)")
  	"\n\tConic, Sph&Ell";
  #define TOL	1e-10
  #define CONV	1e-10
  #define N_ITER	10
  #define I_ITER 20
  #define ITOL 1.e-12
  FORWARD(e_forward); /* ellipsoid */
  	double  ms, sp, cp;
  
  	if (fabs(lp.phi) <= TOL) { xy.x = lp.lam; xy.y = -P->ml0; }
  	else {
  		sp = sin(lp.phi);
  		ms = fabs(cp = cos(lp.phi)) > TOL ? pj_msfn(sp, cp, P->es) / sp : 0.;
  		xy.x = ms * sin(lp.lam *= sp);
  		xy.y = (pj_mlfn(lp.phi, sp, cp, P->en) - P->ml0) + ms * (1. - cos(lp.lam));
  	}
  	return (xy);
  }
  FORWARD(s_forward); /* spheroid */
  	double  cot, E;
  
  	if (fabs(lp.phi) <= TOL) { xy.x = lp.lam; xy.y = P->ml0; }
  	else {
  		cot = 1. / tan(lp.phi);
  		xy.x = sin(E = lp.lam * sin(lp.phi)) * cot;
  		xy.y = lp.phi - P->phi0 + cot * (1. - cos(E));
  	}
  	return (xy);
  }
  INVERSE(e_inverse); /* ellipsoid */
  	xy.y += P->ml0;
  	if (fabs(xy.y) <= TOL) { lp.lam = xy.x; lp.phi = 0.; }
  	else {
  		double r, c, sp, cp, s2ph, ml, mlb, mlp, dPhi;
  		int i;
  
  		r = xy.y * xy.y + xy.x * xy.x;
  		for (lp.phi = xy.y, i = I_ITER; i ; --i) {
  			sp = sin(lp.phi);
  			s2ph = sp * ( cp = cos(lp.phi));
  			if (fabs(cp) < ITOL)
  				I_ERROR;
  			c = sp * (mlp = sqrt(1. - P->es * sp * sp)) / cp;
  			ml = pj_mlfn(lp.phi, sp, cp, P->en);
  			mlb = ml * ml + r;
  			mlp = P->one_es / (mlp * mlp * mlp);
  			lp.phi += ( dPhi =
  				( ml + ml + c * mlb - 2. * xy.y * (c * ml + 1.) ) / (
  				P->es * s2ph * (mlb - 2. * xy.y * ml) / c +
  				2.* (xy.y - ml) * (c * mlp - 1. / s2ph) - mlp - mlp ));
  			if (fabs(dPhi) <= ITOL)
  				break;
  		}
  		if (!i)
  			I_ERROR;
  		c = sin(lp.phi);
  		lp.lam = asin(xy.x * tan(lp.phi) * sqrt(1. - P->es * c * c)) / sin(lp.phi);
  	}
  	return (lp);
  }
  INVERSE(s_inverse); /* spheroid */
  	double B, dphi, tp;
  	int i;
  
  	if (fabs(xy.y = P->phi0 + xy.y) <= TOL) { lp.lam = xy.x; lp.phi = 0.; }
  	else {
  		lp.phi = xy.y;
  		B = xy.x * xy.x + xy.y * xy.y;
  		i = N_ITER;
  		do {
  			tp = tan(lp.phi);
  			lp.phi -= (dphi = (xy.y * (lp.phi * tp + 1.) - lp.phi -
  				.5 * ( lp.phi * lp.phi + B) * tp) /
  				((lp.phi - xy.y) / tp - 1.));
  		} while (fabs(dphi) > CONV && --i);
  		if (! i) I_ERROR;
  		lp.lam = asin(xy.x * tan(lp.phi)) / sin(lp.phi);
  	}
  	return (lp);
  }
  FREEUP; if (P) { if (P->en) pj_dalloc(P->en); pj_dalloc(P); } }
  ENTRY1(poly, en)
  	if (P->es) {
  		if (!(P->en = pj_enfn(P->es))) E_ERROR_0;
  		P->ml0 = pj_mlfn(P->phi0, sin(P->phi0), cos(P->phi0), P->en);
  		P->inv = e_inverse;
  		P->fwd = e_forward;
  	} else {
  		P->ml0 = -P->phi0;
  		P->inv = s_inverse;
  		P->fwd = s_forward;
  	}
  ENDENTRY(P)
  