add numerical recipes library

lib/nr/cpp/recipes/kermom.cpp

@@ -0,0 +1,31 @@
+#include <cmath>
+#include "nr.h"
+using namespace std;
+
+extern DP x;
+
+void NR::kermom(Vec_O_DP &w, const DP y)
+{
+	DP d,df,clog,x2,x3,x4,y2;
+
+	int m=w.size();
+	if (y >= x) {
+		d=y-x;
+		df=2.0*sqrt(d)*d;
+		w[0]=df/3.0;
+		w[1]=df*(x/3.0+d/5.0);
+		w[2]=df*((x/3.0 + 0.4*d)*x + d*d/7.0);
+		w[3]=df*(((x/3.0 + 0.6*d)*x + 3.0*d*d/7.0)*x+d*d*d/9.0);
+	} else {
+		x3=(x2=x*x)*x;
+		x4=x2*x2;
+		y2=y*y;
+		d=x-y;
+		w[0]=d*((clog=log(d))-1.0);
+		w[1] = -0.25*(3.0*x+y-2.0*clog*(x+y))*d;
+		w[2]=(-11.0*x3+y*(6.0*x2+y*(3.0*x+2.0*y))
+			+6.0*clog*(x3-y*y2))/18.0;
+		w[3]=(-25.0*x4+y*(12.0*x3+y*(6.0*x2+y*
+			(4.0*x+3.0*y)))+12.0*clog*(x4-(y2*y2)))/48.0;
+	}
+}