NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO |
|
|
signbit(3) Library Functions Manual signbit(3)
signbit - test sign of a real floating-point number
Math library (libm, -lm)
#include <math.h> int signbit(x); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): signbit(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
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 signbit(-0.0) will return a nonzero value. NaNs and infinities have a sign bit.
The signbit() macro returns nonzero if the sign of x is negative; otherwise it returns zero.
No errors occur.
For an explanation of the terms used in this section, see attributes(7). ┌──────────────────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├──────────────────────────────────────┼───────────────┼─────────┤ │signbit() │ Thread safety │ MT-Safe │ └──────────────────────────────────────┴───────────────┴─────────┘
C11, POSIX.1-2008.
POSIX.1-2001, C99. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).
copysign(3)
Linux man-pages 6.04 2023-03-30 signbit(3)
Pages that refer to this page: copysign(3), fpclassify(3)