1SIGNBIT(3)                    libc math functions                   SIGNBIT(3)
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NAME

6       signbit - test sign of a real floating point number
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SYNOPSIS

9       #include <math.h>
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11       int signbit (X);
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13       Compile with -std=c99; link with -lm.
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DESCRIPTION

16       `signbit'  is a generic macro which can work on all real floating-point
17       types.  It returns a non-zero value if the value of X has its sign  bit
18       set.
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20       This  is  not  the  same  as `x < 0.0', because IEEE 754 floating point
21       allows zero to be signed.  The comparison `-0.0 < 0.0'  is  false,  but
22       `signbit (-0.0)' will return a non-zero value.
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CONFORMING TO

25       C99.  This function is defined in IEC 559 (and the appendix with recom‐
26       mended functions in IEEE 754/IEEE 854).
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SEE ALSO

29       copysign(3)
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33GNU                               2002-08-10                        SIGNBIT(3)
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