Mercurial > gnulib
view lib/log2l.c @ 17363:5a51fb7777a9
sys_select, sys_time: port 2013-01-30 Solaris 2.6 fix to Cygwin
Problem reported by Marco Atzeri in
<http://lists.gnu.org/archive/html/bug-gnulib/2013-03/msg00000.html>.
* lib/sys_select.in.h [HAVE_SYS_SELECT_H && _CYGWIN_SYS_TIME_H]:
Simply delegate to the system <sys/select.h> in this case too.
Also, pay attention to _GL_SYS_SELECT_H_REDIRECT_FROM_SYS_TIME_H only
if OSF/1, since otherwise Cygwin breaks, and it doesn't seem to
be needed on Solaris either.
* lib/sys_time.in.h [_CYGWIN_SYS_TIME_H]:
Simply delgate to the system <sys/time.h> in this case.
author | Paul Eggert <eggert@cs.ucla.edu> |
---|---|
date | Tue, 19 Mar 2013 09:08:47 -0700 |
parents | e542fd46ad6f |
children | 344018b6e5d7 |
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/* Base 2 logarithm. Copyright (C) 2011-2013 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/>. */ #include <config.h> /* Specification. */ #include <math.h> #if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE long double log2l (long double x) { return log2 (x); } #else /* Best possible approximation of log(2) as a 'long double'. */ #define LOG2 0.693147180559945309417232121458176568075L /* Best possible approximation of 1/log(2) as a 'long double'. */ #define LOG2_INVERSE 1.44269504088896340735992468100189213743L /* sqrt(0.5). */ #define SQRT_HALF 0.707106781186547524400844362104849039284L long double log2l (long double x) { if (isnanl (x)) return x; if (x <= 0.0L) { if (x == 0.0L) /* Return -Infinity. */ return - HUGE_VALL; else { /* Return NaN. */ #if defined _MSC_VER || (defined __sgi && !defined __GNUC__) static long double zero; return zero / zero; #else return 0.0L / 0.0L; #endif } } /* Decompose x into x = 2^e * y where e is an integer, 1/2 < y < 2. Then log2(x) = e + log2(y) = e + log(y)/log(2). */ { int e; long double y; y = frexpl (x, &e); if (y < SQRT_HALF) { y = 2.0L * y; e = e - 1; } return (long double) e + logl (y) * LOG2_INVERSE; } } #endif