using System;
public class hydrogen{

public static double Fe(double e, double r,double rmin=1e-3){

if(r<rmin) return r-r*r;

/* -(1/2)f'' - (1/r)f = e f */
Func<double,vector,vector> swave = (x,y)=>new vector(y[1], 2*(-1/x-e)*y[0]);

vector yrmin = new vector(rmin-rmin*rmin, 1-2*rmin);
vector yrmax = ODE.driver(swave,rmin,yrmin,r,acc:1e-3,eps:1e-3,h:1e-2);
return yrmax[0];

}

}//class