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Manual Reference Pages  - SIGNBIT (3)

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signbit - test sign of a real floating point number

CONTENTS

Synopsis
Description

#include <math.h>

int signbit (X);

‘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.

This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).

copysign(3)

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