add numerical recipes library

lib/nr/ansi/recipes/sphbes.c

@@ -0,0 +1,21 @@
+
+#include <math.h>
+#define RTPIO2 1.2533141
+
+void sphbes(int n, float x, float *sj, float *sy, float *sjp, float *syp)
+{
+	void bessjy(float x, float xnu, float *rj, float *ry, float *rjp,
+		float *ryp);
+	void nrerror(char error_text[]);
+	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