add numerical recipes library

lib/nr/cpp/recipes/pccheb.cpp

@@ -0,0 +1,22 @@
+#include "nr.h"
+
+void NR::pccheb(Vec_I_DP &d, Vec_O_DP &c)
+{
+	int j,jm,jp,k;
+	DP fac,pow;
+
+	int n=d.size();
+	pow=1.0;
+	c[0]=2.0*d[0];
+	for (k=1;k<n;k++) {
+		c[k]=0.0;
+		fac=d[k]/pow;
+		jm=k;
+		jp=1;
+		for (j=k;j>=0;j-=2,jm--,jp++) {
+			c[j] += fac;
+			fac *= DP(jm)/DP(jp);
+		}
+		pow += pow;
+	}
+}