add numerical recipes library

lib/nr/k_and_r/recipes/sphbes.c

@@ -0,0 +1,22 @@
+
+#include <math.h>
+#define RTPIO2 1.2533141
+
+void sphbes(n,x,sj,sy,sjp,syp)
+float *sj,*sjp,*sy,*syp,x;
+int n;
+{
+	void bessjy();
+	void nrerror();
+	float factor,order,rj,rjp,ry,ryp;
+
+	if (n < 0 || x <= 0.0) nrerror("bad arguments in sphbes");
+	order=n+0.5;
+	bessjy(x,order,&rj,&ry,&rjp,&ryp);
+	factor=RTPIO2/sqrt(x);
+	*sj=factor*rj;
+	*sy=factor*ry;
+	*sjp=factor*rjp-(*sj)/(2.0*x);
+	*syp=factor*ryp-(*sy)/(2.0*x);
+}
+#undef RTPIO2