signbit(3) - phpMan

SIGNBIT(3)                 Linux Programmer's Manual                SIGNBIT(3)
NAME
       signbit - test sign of a real floating-point number
SYNOPSIS
       #include <math.h>
       int signbit(x);
       Link with -lm.
   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
       signbit():
           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
DESCRIPTION
       signbit()  is a generic macro which can work on all real floating-point
       types.  It returns a nonzero value if the value of x has its  sign  bit
       set.
       This is not the same as x < 0.0, because IEEE 754 floating point allows
       zero to be signed.  The comparison -0.0  <  0.0  is  false,  but  sign-
       bit(-0.0) will return a nonzero value.
       NaNs and infinities have a sign bit.
RETURN VALUE
       The  signbit() macro returns nonzero if the sign of x is negative; oth-
       erwise it returns zero.
ERRORS
       No errors occur.
ATTRIBUTES
       For  an  explanation  of  the  terms  used   in   this   section,   see
       attributes(7).
       +----------+---------------+---------+
       |Interface | Attribute     | Value   |
       +----------+---------------+---------+
       |signbit() | Thread safety | MT-Safe |
       +----------+---------------+---------+
CONFORMING TO
       POSIX.1-2001,  POSIX.1-2008,  C99.  This function is defined in IEC 559
       (and the appendix with recommended functions in IEEE 754/IEEE 854).
SEE ALSO
       copysign(3)
COLOPHON
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       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at
       https://www.kernel.org/doc/man-pages/.
GNU                               2017-09-15                        SIGNBIT(3)