add numerical recipes library

lib/nr/k_and_r/recipes/julday.c

@@ -0,0 +1,27 @@
+
+#include <math.h>
+#define IGREG (15+31L*(10+12L*1582))
+
+long julday(mm,id,iyyy)
+int id,iyyy,mm;
+{
+	void nrerror();
+	long jul;
+	int ja,jy=iyyy,jm;
+
+	if (jy == 0) nrerror("julday: there is no year zero.");
+	if (jy < 0) ++jy;
+	if (mm > 2) {
+		jm=mm+1;
+	} else {
+		--jy;
+		jm=mm+13;
+	}
+	jul = (long) (floor(365.25*jy)+floor(30.6001*jm)+id+1720995);
+	if (id+31L*(mm+12L*iyyy) >= IGREG) {
+		ja=(int)(0.01*jy);
+		jul += 2-ja+(int) (0.25*ja);
+	}
+	return jul;
+}
+#undef IGREG