Merge commit 'a39d4083cab589d7cd6a13e8a4b8db8875261d75'

[gnulib.git] / lib / atanl.c

diff --git a/lib/atanl.c b/lib/atanl.c
index 2959e0b..88284a6 100644 (file)
--- a/lib/atanl.c
+++ b/lib/atanl.c
@@ -1,6 +1,38 @@
-/*                                                     s_atanl.c
+/* Copyright 2001 by Stephen L. Moshier <moshier@na-net.ornl.gov>
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <math.h>
+
+#if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
+
+long double
+atanl (long double x)
+{
+  return atan (x);
+}
+
+#else
+
+/* Code based on glibc/sysdeps/ieee754/ldbl-128/s_atanl.c.  */
+
+/*                                                      s_atanl.c
  *
- *     Inverse circular tangent for 128-bit long double precision
+ *      Inverse circular tangent for 128-bit long double precision
  *      (arctangent)
  *
  *
@@ -42,12 +74,6 @@
  *
  */
 
-/* Copyright 2001 by Stephen L. Moshier <moshier@na-net.ornl.gov>  */
-
-#include "mathl.h"
-
-#include <math.h>
-
 /* arctan(k/8), k = 0, ..., 82 */
 static const long double atantbl[84] = {
   0.0000000000000000000000000000000000000000E0L,
@@ -161,19 +187,25 @@ atanl (long double x)
   int k, sign;
   long double t, u, p, q;
 
-  sign = (x < 0) ? -1 : 1;
-
   /* Check for zero or NaN.  */
-  if (x != x || x == 0.0)
+  if (isnanl (x) || x == 0.0)
     return x + x;
 
-  /* Check for infinity.  */
+  sign = x < 0.0;
+
   if (x + x == x)
-    return sign * atantbl[83];
+    {
+      /* Infinity. */
+      if (sign)
+        return -atantbl[83];
+      else
+        return atantbl[83];
+    }
 
-  x *= sign;
+  if (sign)
+      x = -x;
 
-  if (x >= 10.25) /* 10.25 */
+  if (x >= 10.25)
     {
       k = 83;
       t = -1.0/x;
@@ -181,7 +213,7 @@ atanl (long double x)
   else
     {
       /* Index of nearest table element.
-        Roundoff to integer is asymmetrical to avoid cancellation when t < 0
+         Roundoff to integer is asymmetrical to avoid cancellation when t < 0
          (cf. fdlibm). */
       k = 8.0 * x + 0.25;
       u = 0.125 * k;
@@ -196,5 +228,11 @@ atanl (long double x)
   u = t * u * p / q  +  t;
 
   /* arctan x = arctan u  +  arctan t */
-  return sign * (atantbl[k] + u);
+  u = atantbl[k] + u;
+  if (sign)
+    return (-u);
+  else
+    return u;
 }
+
+#endif