1SIGNBIT(3) Linux Programmer's Manual SIGNBIT(3)
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6 signbit - test sign of a real floating-point number
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9 #include <math.h>
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11 int signbit(x);
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13 Link with -lm.
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15 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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17 signbit(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99
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20 signbit() is a generic macro which can work on all real floating-point
21 types. It returns a non-zero value if the value of x has its sign bit
22 set.
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24 This is not the same as x < 0.0, because IEEE 754 floating point allows
25 zero to be signed. The comparison -0.0 < 0.0 is false, but sign‐
26 bit(-0.0) will return a non-zero value.
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28 NaNs and infinities have a sign bit.
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31 The signbit() macro returns non-zero if the sign of x is negative; oth‐
32 erwise it returns zero.
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35 No errors occur.
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38 C99, POSIX.1-2001. This function is defined in IEC 559 (and the appen‐
39 dix with recommended functions in IEEE 754/IEEE 854).
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42 copysign(3)
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45 This page is part of release 3.22 of the Linux man-pages project. A
46 description of the project, and information about reporting bugs, can
47 be found at http://www.kernel.org/doc/man-pages/.
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51GNU 2008-08-05 SIGNBIT(3)