chebyshev.cpp

double chebyshev_per2(int n, double x)
{
	double a = 1.0, b = x;
#define DO(i) case i: { const double t = b; b = 2.0 * x * b - a; a = t; }
	switch (n) { DO(9) DO(8) DO(7) DO(6) DO(5) DO(4) DO(3) DO(2) DO(1) }
	return a;
}