--- /dev/null
+/* Floating-point exponent.
+ Copyright (C) 2012 Free Software Foundation, Inc.
+
+ 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/>. */
+
+#if ! (defined USE_LONG_DOUBLE || defined USE_FLOAT)
+# include <config.h>
+#endif
+
+/* Specification. */
+#include <math.h>
+
+#ifdef USE_LONG_DOUBLE
+# define LOGB logbl
+# define DOUBLE long double
+# define L_(literal) literal##L
+# define HUGEVAL HUGE_VALL
+# define FREXP frexpl
+# define ISNAN isnanl
+#elif ! defined USE_FLOAT
+# define LOGB logb
+# define DOUBLE double
+# define L_(literal) literal
+# define HUGEVAL HUGE_VAL
+# define FREXP frexp
+# define ISNAN isnand
+#else /* defined USE_FLOAT */
+# define LOGB logbf
+# define DOUBLE float
+# define L_(literal) literal##f
+# define HUGEVAL HUGE_VALF
+# define FREXP frexpf
+# define ISNAN isnanf
+#endif
+
+DOUBLE
+LOGB (DOUBLE x)
+{
+ if (isfinite (x))
+ {
+ if (x == L_(0.0))
+ /* Return -Infinity. */
+ return - HUGEVAL;
+ else
+ {
+ int e;
+
+ (void) FREXP (x, &e);
+ return (DOUBLE) (e - 1);
+ }
+ }
+ else
+ {
+ if (ISNAN (x))
+ return x; /* NaN */
+ else
+ /* Return +Infinity. */
+ return HUGEVAL;
+ }
+}