using static System.Math;
public static partial class specfunc{

public static double gamma(double x){
/// single precision gamma function (Gergo Nemes, from Wikipedia)
if(x<0)return PI/Sin(PI*x)/gamma(1-x);
if(x<9)return gamma(x+1)/x;
double lngamma=x*Log(x+1/(12*x-1/x/10))-x+Log(2*PI/x)/2;
return Exp(lngamma);
}

}