diff options
author | Bruno Haible <bruno@clisp.org> | 2012-04-03 02:51:42 +0200 |
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committer | Bruno Haible <bruno@clisp.org> | 2012-04-03 13:58:10 +0200 |
commit | 77e408383e7944caaf77cb068e670238aa7ee905 (patch) | |
tree | 51b65542ea5dd5fefd8a9d0e74e7829d4c2e02d9 /lib/logb.c | |
parent | cd2e4d4bfbf4bfbc8d2155969a63605759f8f243 (diff) | |
download | gnulib-77e408383e7944caaf77cb068e670238aa7ee905.tar.gz |
logb: Provide replacement and workarounds.
* lib/math.in.h (logb): Ensure declaration. Replace if REPLACE_LOGB
is 1.
* lib/logb.c: New file.
* m4/logb.m4 (gl_FUNC_LOGB_WORKS): New macro.
(gl_FUNC_LOGB): Invoke it. Set HAVE_LOGB, REPLACE_LOGB.
* m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize REPLACE_LOGB.
* modules/math (Makefile.am): Substitute REPLACE_LOGB.
* modules/logb (Files): Add lib/logb.c.
(Depends-on): Add isfinite, frexp, isnand.
(configure.ac): Compile the replacement code logb.c if needed.
* tests/test-math-c++.cc: Check the declaration of logb.
* doc/posix-functions/logb.texi: Mention the replacement and the bug
with subnormal numbers.
Diffstat (limited to 'lib/logb.c')
-rw-r--r-- | lib/logb.c | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/lib/logb.c b/lib/logb.c new file mode 100644 index 0000000000..d56be557a7 --- /dev/null +++ b/lib/logb.c @@ -0,0 +1,71 @@ +/* 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; + } +} |