// Create driver/stepper that treats real and imaginary parts separately before recombining
public static Tuple<List<complex>, List<complex>, int, List<double>> cdrive_split(Func<complex,complex, complex> f, complex a, complex b, complex ya, complex h= default(complex), double acc=1e-4, double eps=1e-4, int nmax=100000){
// Return lists. I use lists because arrays and vectors don't play nice with complex
List<complex> zs = new List<complex>(){a};
List<complex> ys = new List<complex>(){ya};
List<double> errs = new List<double>();
int nsteps=0;
complex ar = new complex(a.Re,0); complex ai = new complex(0,a.Im);
complex br = new complex(b.Re,0); complex bi = new complex(0,b.Im);
if(h.Equals(default(complex)))h=(b-a)/1000;
double dist = abs(b-a);
double newdist = abs(b-a)-acc;
do{
if(abs(b-a)<acc)break; // End statement
if(nsteps>nmax){
Write("Error: Did not converge within iteration limit\n");
break;
}
if(abs(a+h)>abs(b-a))h=b-a;
nsteps++;
double err=0; // = new complex();
complex y_re = crkstep45_single(f,ar,ya,h,err);
double tol_re = abs(sqrt(h/(br-ar)))*(eps*abs(y_re)+acc);
complex y_im = crkstep45_single(f,ai,ya,h,err);
double tol_im = abs(sqrt(h/(bi-ai)))*(eps*abs(y_im)+acc);
complex y_next = new complex(y_re.Re, y_im.Im);
double tol = Sqrt(Pow(tol_re,2)+Pow(tol_im,2));
if(err==0)err=tol/4;
// Relative error, and checking for bad steps
double rel_arr = tol/err;
bool crap = false;
if(rel_arr<1.0)crap=true;
if(!crap){
dist = abs(b-a);
a+=h;
newdist = abs(b-a);
ya = y_next;
zs.Add(a);
ys.Add(ya);
errs.Add(rel_arr);
}
// Calculating the next step size, using eq. 40
h = h*(Pow(rel_arr,0.25)*0.95);
}while(newdist<dist); //End of while-loop
return Tuple.Create(zs, ys, nsteps, errs);
}
