add numerical recipes library

lib/nr/cpp/recipes/fredex.cpp

@@ -0,0 +1,28 @@
+#include <iostream>
+#include <iomanip>
+#include <cmath>
+#include "nr.h"
+using namespace std;
+
+int main(void)	// Program fredex
+{
+	const int N=40;
+	const DP PI=3.141592653589793238;
+	int j;
+	DP d,x;
+	Vec_INT indx(N);
+	Vec_DP g(N);
+	Mat_DP a(N,N);
+
+	NR::quadmx(a);
+	NR::ludcmp(a,indx,d);
+	for (j=0;j<N;j++)
+		g[j]=sin(j*PI/(N-1));
+	NR::lubksb(a,indx,g);
+	for (j=0;j<N;j++) {
+		x=j*PI/(N-1);
+		cout << fixed << setprecision(2) << setw(6) << (j+1);
+		cout << setprecision(6) << setw(13) << x << setw(13) << g[j] << endl;
+	}
+	return 0;
+}