/* Round towards zero.
- Copyright (C) 2007 Free Software Foundation, Inc.
+ Copyright (C) 2007, 2010-2014 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. */
-#include <config.h>
+#if ! defined USE_LONG_DOUBLE
+# include <config.h>
+#endif
/* Specification. */
#include <math.h>
#include <float.h>
-/* 2^(DBL_MANT_DIG-1). */
-static const double TWO_MANT_DIG =
- /* Assume DBL_MANT_DIG <= 4 * 31.
+#undef MIN
+
+#ifdef USE_LONG_DOUBLE
+# define FUNC truncl
+# define DOUBLE long double
+# define MANT_DIG LDBL_MANT_DIG
+# define MIN LDBL_MIN
+# define L_(literal) literal##L
+#elif ! defined USE_FLOAT
+# define FUNC trunc
+# define DOUBLE double
+# define MANT_DIG DBL_MANT_DIG
+# define MIN DBL_MIN
+# define L_(literal) literal
+#else /* defined USE_FLOAT */
+# define FUNC truncf
+# define DOUBLE float
+# define MANT_DIG FLT_MANT_DIG
+# define MIN FLT_MIN
+# define L_(literal) literal##f
+#endif
+
+/* -0.0. See minus-zero.h. */
+#if defined __hpux || defined __sgi || defined __ICC
+# define MINUS_ZERO (-MIN * MIN)
+#else
+# define MINUS_ZERO L_(-0.0)
+#endif
+
+/* MSVC with option -fp:strict refuses to compile constant initializers that
+ contain floating-point operations. Pacify this compiler. */
+#ifdef _MSC_VER
+# pragma fenv_access (off)
+#endif
+
+/* 2^(MANT_DIG-1). */
+static const DOUBLE TWO_MANT_DIG =
+ /* Assume MANT_DIG <= 5 * 31.
Use the identity
- n = floor(n/4) + floor((n+1)/4) + floor((n+2)/4) + floor((n+3)/4). */
- (double) (1U << ((DBL_MANT_DIG - 1) / 4))
- * (double) (1U << ((DBL_MANT_DIG - 1 + 1) / 4))
- * (double) (1U << ((DBL_MANT_DIG - 1 + 2) / 4))
- * (double) (1U << ((DBL_MANT_DIG - 1 + 3) / 4));
+ n = floor(n/5) + floor((n+1)/5) + ... + floor((n+4)/5). */
+ (DOUBLE) (1U << ((MANT_DIG - 1) / 5))
+ * (DOUBLE) (1U << ((MANT_DIG - 1 + 1) / 5))
+ * (DOUBLE) (1U << ((MANT_DIG - 1 + 2) / 5))
+ * (DOUBLE) (1U << ((MANT_DIG - 1 + 3) / 5))
+ * (DOUBLE) (1U << ((MANT_DIG - 1 + 4) / 5));
-double
-trunc (double x)
+DOUBLE
+FUNC (DOUBLE x)
{
/* The use of 'volatile' guarantees that excess precision bits are dropped
at each addition step and before the following comparison at the caller's
compliant by default, to avoid that the results become platform and compiler
option dependent. 'volatile' is a portable alternative to gcc's
-ffloat-store option. */
- volatile double y = x;
- volatile double z = y;
+ volatile DOUBLE y = x;
+ volatile DOUBLE z = y;
- if (z > 0)
+ 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 -= 1.0;
+ /* For 0 < x < 1, return +0.0 even if the current rounding mode is
+ FE_DOWNWARD. */
+ if (z < L_(1.0))
+ z = L_(0.0);
+ /* Avoid rounding errors for values near 2^k, where k >= MANT_DIG-1. */
+ else 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 < 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 += 1.0;
+ /* For -1 < x < 0, return -0.0 regardless of the current rounding
+ mode. */
+ if (z > L_(-1.0))
+ z = MINUS_ZERO;
+ /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1. */
+ else 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;
}
projects / gnulib.git / blobdiff