hypgeo.c

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#include <math.h>
#include "complex.h"
#define NRANSI
#include "nrutil.h"
#define EPS 1.0e-6

fcomplex aa,bb,cc,z0,dz;

int kmax,kount;
float *xp,**yp,dxsav;

fcomplex hypgeo(fcomplex a, fcomplex b, fcomplex c, fcomplex z)
{
	void bsstep(float y[], float dydx[], int nv, float *xx, float htry,
		float eps, float yscal[], float *hdid, float *hnext,
		void (*derivs)(float, float [], float []));
	void hypdrv(float s, float yy[], float dyyds[]);
	void hypser(fcomplex a, fcomplex b, fcomplex c, fcomplex z,
		fcomplex *series, fcomplex *deriv);
	void odeint(float ystart[], int nvar, float x1, float x2,
		float eps, float h1, float hmin, int *nok, int *nbad,
		void (*derivs)(float, float [], float []),
		void (*rkqs)(float [], float [], int, float *, float, float,
		float [], float *, float *, void (*)(float, float [], float [])));
	int nbad,nok;
	fcomplex ans,y[3];
	float *yy;

	kmax=0;
	if (z.r*z.r+z.i*z.i <= 0.25) {
		hypser(a,b,c,z,&ans,&y[2]);
		return ans;
	}
	else if (z.r < 0.0) z0=Complex(-0.5,0.0);
	else if (z.r <= 1.0) z0=Complex(0.5,0.0);
	else z0=Complex(0.0,z.i >= 0.0 ? 0.5 : -0.5);
	aa=a;
	bb=b;
	cc=c;
	dz=Csub(z,z0);
	hypser(aa,bb,cc,z0,&y[1],&y[2]);
	yy=vector(1,4);
	yy[1]=y[1].r;
	yy[2]=y[1].i;
	yy[3]=y[2].r;
	yy[4]=y[2].i;
	odeint(yy,4,0.0,1.0,EPS,0.1,0.0001,&nok,&nbad,hypdrv,bsstep);
	y[1]=Complex(yy[1],yy[2]);
	free_vector(yy,1,4);
	return y[1];
}
#undef EPS
#undef NRANSI