add numerical recipes library

lib/nr/cpp/recipes/chder.cpp

@@ -0,0 +1,15 @@
+#include "nr.h"
+
+void NR::chder(const DP a, const DP b, Vec_I_DP &c, Vec_O_DP &cder, const int n)
+{
+	int j;
+	DP con;
+
+	cder[n-1]=0.0;
+	cder[n-2]=2*(n-1)*c[n-1];
+	for (j=n-2;j>0;j--)
+		cder[j-1]=cder[j+1]+2*j*c[j];
+	con=2.0/(b-a);
+	for (j=0;j<n;j++)
+		cder[j] *= con;
+}