NAME
signbit - test sign of a real floating-point number SYNOPSIS
#include
int signbit(x); Link with -lm. Feature Test Macro Requirements for glibc (see featuretestmacros(7)): signbit(): XOPENSOURCE >= 600 || ISOC99SOURCE || POSIXCSOURCE >= 200112L;
or cc -std=c99 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
C99, POSIX.1-2001. This function is defined in IEC 559 (and the appen‐ dix with recommended functions in IEEE 754/IEEE 854). SEE ALSO copysign(3) COLOPHON
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GNU 2013-07-04 SIGNBIT(3)