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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:40:15 +0000 |
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| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-15 19:40:15 +0000 |
| commit | 399644e47874bff147afb19c89228901ac39340e (patch) | |
| tree | 1c4c0b733f4c16b5783b41bebb19194a9ef62ad1 /man3/signbit.3 | |
| parent | Initial commit. (diff) | |
| download | manpages-399644e47874bff147afb19c89228901ac39340e.tar.xz manpages-399644e47874bff147afb19c89228901ac39340e.zip | |
Adding upstream version 6.05.01.upstream/6.05.01
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'man3/signbit.3')
| -rw-r--r-- | man3/signbit.3 | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/man3/signbit.3 b/man3/signbit.3 new file mode 100644 index 0000000..5dddad6 --- /dev/null +++ b/man3/signbit.3 @@ -0,0 +1,80 @@ +'\" t +.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de) +.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk +.\" <mtk.manpages@gmail.com> +.\" +.\" SPDX-License-Identifier: GPL-1.0-or-later +.\" +.\" Based on glibc infopages, copyright Free Software Foundation +.\" +.TH signbit 3 2023-07-20 "Linux man-pages 6.05.01" +.SH NAME +signbit \- test sign of a real floating-point number +.SH LIBRARY +Math library +.RI ( libm ", " \-lm ) +.SH SYNOPSIS +.nf +.B "#include <math.h>" +.PP +.BI "int signbit(" x ");" +.fi +.PP +.RS -4 +Feature Test Macro Requirements for glibc (see +.BR feature_test_macros (7)): +.RE +.PP +.BR signbit (): +.nf + _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L +.fi +.SH DESCRIPTION +.BR signbit () +is a generic macro which can work on all real floating-point types. +It returns a nonzero value if the value of +.I x +has its sign bit set. +.PP +This is not the same as +.IR "x < 0.0" , +because IEEE 754 floating point allows zero to be signed. +The comparison +.I \-0.0\~<\~0.0 +is false, but +.I signbit(\-0.0) +will return a nonzero value. +.PP +NaNs and infinities have a sign bit. +.SH RETURN VALUE +The +.BR signbit () +macro returns nonzero if the sign of +.I x +is negative; otherwise it returns zero. +.SH ERRORS +No errors occur. +.SH ATTRIBUTES +For an explanation of the terms used in this section, see +.BR attributes (7). +.TS +allbox; +lbx lb lb +l l l. +Interface Attribute Value +T{ +.na +.nh +.BR signbit () +T} Thread safety MT-Safe +.TE +.sp 1 +.SH STANDARDS +C11, POSIX.1-2008. +.SH HISTORY +POSIX.1-2001, C99. +.PP +This function is defined in IEC 559 (and the appendix with +recommended functions in IEEE 754/IEEE 854). +.SH SEE ALSO +.BR copysign (3) |