add numerical recipes library

lib/nr/cpp/recipes/ddpoly.cpp

@@ -0,0 +1,22 @@
+#include "nr.h"
+
+void NR::ddpoly(Vec_I_DP &c, const DP x, Vec_O_DP &pd)
+{
+	int nnd,j,i;
+	DP cnst=1.0;
+
+	int nc=c.size()-1;
+	int nd=pd.size()-1;
+	pd[0]=c[nc];
+	for (j=1;j<nd+1;j++) pd[j]=0.0;
+	for (i=nc-1;i>=0;i--) {
+		nnd=(nd < (nc-i) ? nd : nc-i);
+		for (j=nnd;j>0;j--)
+			pd[j]=pd[j]*x+pd[j-1];
+		pd[0]=pd[0]*x+c[i];
+	}
+	for (i=2;i<nd+1;i++) {
+		cnst *= i;
+		pd[i] *= cnst;
+	}
+}