add numerical recipes library

lib/nr/cpp/recipes/zrhqr.cpp

@@ -0,0 +1,27 @@
+#include <complex>
+#include "nr.h"
+using namespace std;
+
+void NR::zrhqr(Vec_I_DP &a, Vec_O_CPLX_DP &rt)
+{
+	int j,k;
+	complex<DP> x;
+
+	int m=a.size()-1;
+	Mat_DP hess(m,m);
+	for (k=0;k<m;k++) {
+		hess[0][k] = -a[m-k-1]/a[m];
+		for (j=1;j<m;j++) hess[j][k]=0.0;
+		if (k != m-1) hess[k+1][k]=1.0;
+	}
+	balanc(hess);
+	hqr(hess,rt);
+	for (j=1;j<m;j++) {
+		x=rt[j];
+		for (k=j-1;k>=0;k--) {
+			if (real(rt[k]) <= real(x)) break;
+			rt[k+1]=rt[k];
+		}
+		rt[k+1]=x;
+	}
+}