signbit(3) Library Functions Manual signbit(3) NAME signbit - test sign of a real floating-point number LIBRARY Math library (libm, -lm) SYNOPSIS #include <math.h> int signbit(x); 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 at- tributes(7). ┌────────────────────────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├────────────────────────────────────────────┼───────────────┼─────────┤ │signbit() │ Thread safety │ MT-Safe │ └────────────────────────────────────────────┴───────────────┴─────────┘ STANDARDS 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) Linux man-pages 6.03 2022-12-15 signbit(3)
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