# HG changeset patch
# User John W. Eaton <jwe@octave.org>
# Date 1326388233 18000
# Node ID 35ce1eab7400af0b1faf404e3b863b0036eaa93c
# Parent  1eeb3a8d5708f72240185558a7f8c52933b7d1f6
besseli: use special case for negative integer orders

* lo-specfun.cc (zbesi): Special case for negative integer orders.

diff -r 1eeb3a8d5708 -r 35ce1eab7400 liboctave/lo-specfun.cc
--- a/liboctave/lo-specfun.cc	Wed Jan 11 12:38:20 2012 -0500
+++ b/liboctave/lo-specfun.cc	Thu Jan 12 12:10:33 2012 -0500
@@ -852,6 +852,15 @@
 
       retval = bessel_return_value (Complex (yr, yi), ierr);
     }
+  else if (is_integer_value (alpha))
+    {
+      // zbesi can overflow as z->0, and cause troubles for generic case below
+      alpha = -alpha;
+      Complex tmp = zbesi (z, alpha, kode, ierr);
+      if ((static_cast <long> (alpha)) & 1)
+        tmp = - tmp;
+      retval = bessel_return_value (tmp, ierr);
+    }
   else
     {
       alpha = -alpha;