signbit — test sign of a real floating point number
#include <math.h>
int
signbit( |
X) ; |
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`signbit' is a generic macro which can work on all real floating-point types. It returns a non-zero 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 non-zero value.
C99. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).