public static Func <double, double> Get2(int n)
{
double One(double x) => 1;
if (n == 0)
{
return(One);
}
double X(double x) => x;
if (n == 1)
{
return(X);
}
n = n - 1;
var pow2 = (int)Math.Pow(2, Math.Floor(Math.Log(n, 2)));
double Sobolev(double x)
{
return(Walsh.Get(n - pow2)(x) * W12(pow2 * x) / pow2);
}
return(Sobolev);
}
public static Func <double, double> Get(int n)
{
double One(double x) => 1;
if (n == 0)
{
return(One);
}
var nodesCount = (int)Math.Pow(2, (int)Math.Ceiling(Math.Log(n, 2)) + 6);
var nodes = Enumerable.Range(0, nodesCount).Select(j => j * 1.0 / nodesCount);
double Sobolev(double x)
{
return(Integrals.Rectangular(Walsh.Get(n - 1), nodes.Where(node => node <= x).ToArray(),
Integrals.RectType.Center));
}
return(Sobolev);
}