add numerical recipes library

lib/nr/cpp/recipes/bnldev.cpp

@@ -0,0 +1,53 @@
+#include <cmath>
+#include "nr.h"
+using namespace std;
+
+DP NR::bnldev(const DP pp, const int n, int &idum)
+{
+	const DP PI=3.141592653589793238;
+	int j;
+	static int nold=(-1);
+	DP am,em,g,angle,p,bnl,sq,t,y;
+	static DP pold=(-1.0),pc,plog,pclog,en,oldg;
+
+	p=(pp <= 0.5 ? pp : 1.0-pp);
+	am=n*p;
+	if (n < 25) {
+		bnl=0.0;
+		for (j=0;j<n;j++)
+			if (ran1(idum) < p) ++bnl;
+	} else if (am < 1.0) {
+		g=exp(-am);
+		t=1.0;
+		for (j=0;j<=n;j++) {
+			t *= ran1(idum);
+			if (t < g) break;
+		}
+		bnl=(j <= n ? j : n);
+	} else {
+		if (n != nold) {
+			en=n;
+			oldg=gammln(en+1.0);
+			nold=n;
+		} if (p != pold) {
+			pc=1.0-p;
+			plog=log(p);
+			pclog=log(pc);
+			pold=p;
+		}
+		sq=sqrt(2.0*am*pc);
+		do {
+			do {
+				angle=PI*ran1(idum);
+				y=tan(angle);
+				em=sq*y+am;
+			} while (em < 0.0 || em >= (en+1.0));
+			em=floor(em);
+			t=1.2*sq*(1.0+y*y)*exp(oldg-gammln(em+1.0)
+				-gammln(en-em+1.0)+em*plog+(en-em)*pclog);
+		} while (ran1(idum) > t);
+		bnl=em;
+	}
+	if (p != pp) bnl=n-bnl;
+	return bnl;
+}