add numerical recipes library

lib/nr/k_and_r/recipes/ddpoly.c

@@ -0,0 +1,21 @@
+
+void ddpoly(c,nc,x,pd,nd)
+float c[],pd[],x;
+int nc,nd;
+{
+	int nnd,j,i;
+	float cnst=1.0;
+
+	pd[0]=c[nc];
+	for (j=1;j<=nd;j++) pd[j]=0.0;
+	for (i=nc-1;i>=0;i--) {
+		nnd=(nd < (nc-i) ? nd : nc-i);
+		for (j=nnd;j>=1;j--)
+			pd[j]=pd[j]*x+pd[j-1];
+		pd[0]=pd[0]*x+c[i];
+	}
+	for (i=2;i<=nd;i++) {
+		cnst *= i;
+		pd[i] *= cnst;
+	}
+}