X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Ftrunc.c;h=31e1e77d285ae042d463e080df708bd4b8a34144;hb=1b5bc6ed268e3f86e5fab50eb42794400e29ea2f;hp=40673a728a99d0166d7ffbd3241aea9e5cdaab7d;hpb=152e99575c43cc17bbb11ecd32d38418c1d68dc6;p=gnulib.git

diff --git a/lib/trunc.c b/lib/trunc.c
index 40673a728..31e1e77d2 100644
--- a/lib/trunc.c
+++ b/lib/trunc.c
@@ -1,19 +1,18 @@
 /* Round towards zero.
-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009, 2010 Free Software Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or modify
+   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 2, or (at your option)
-   any later version.
+   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, write to the Free Software Foundation,
-   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 /* Written by Bruno Haible <bruno@clisp.org>, 2007.  */
 
@@ -42,7 +41,7 @@
 #endif
 
 /* 2^(MANT_DIG-1).  */
-static const double TWO_MANT_DIG =
+static const DOUBLE TWO_MANT_DIG =
   /* Assume MANT_DIG <= 5 * 31.
      Use the identity
        n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5).  */
@@ -66,21 +65,29 @@ FUNC (DOUBLE x)
 
   if (z > L_(0.0))
     {
-      /* Round to the next integer (nearest or up or down, doesn't matter).  */
-      z += TWO_MANT_DIG;
-      z -= TWO_MANT_DIG;
-      /* Enforce rounding down.  */
-      if (z > y)
-	z -= L_(1.0);
+      /* Avoid rounding errors for values near 2^k, where k >= MANT_DIG-1.  */
+      if (z < TWO_MANT_DIG)
+        {
+          /* Round to the next integer (nearest or up or down, doesn't matter).  */
+          z += TWO_MANT_DIG;
+          z -= TWO_MANT_DIG;
+          /* Enforce rounding down.  */
+          if (z > y)
+            z -= L_(1.0);
+        }
     }
   else if (z < L_(0.0))
     {
-      /* Round to the next integer (nearest or up or down, doesn't matter).  */
-      z -= TWO_MANT_DIG;
-      z += TWO_MANT_DIG;
-      /* Enforce rounding up.  */
-      if (z < y)
-	z += L_(1.0);
+      /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1.  */
+      if (z > - TWO_MANT_DIG)
+        {
+          /* Round to the next integer (nearest or up or down, doesn't matter).  */
+          z -= TWO_MANT_DIG;
+          z += TWO_MANT_DIG;
+          /* Enforce rounding up.  */
+          if (z < y)
+            z += L_(1.0);
+        }
     }
   return z;
 }