add numerical recipes library

2025-09-12 18:55:25 +09:00
parent d4dff245bd
commit 2c75620ec9
1344 changed files with 63869 additions and 0 deletions
--- a/lib/nr/cpp/recipes/bessk.cpp
+++ b/lib/nr/cpp/recipes/bessk.cpp
@@ -0,0 +1,18 @@
+#include "nr.h"
+
+DP NR::bessk(const int n, const DP x)
+{
+	int j;
+	DP bk,bkm,bkp,tox;
+
+	if (n < 2) nrerror("Index n less than 2 in bessk");
+	tox=2.0/x;
+	bkm=bessk0(x);
+	bk=bessk1(x);
+	for (j=1;j<n;j++) {
+		bkp=bkm+j*tox*bk;
+		bkm=bk;
+		bk=bkp;
+	}
+	return bk;
+}