copysign(3)

1copysign(3)                Library Functions Manual                copysign(3)
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NAME

6       copysign, copysignf, copysignl - copy sign of a number
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LIBRARY

9       Math library (libm, -lm)
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SYNOPSIS

12       #include <math.h>
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14       double copysign(double x, double y);
15       float copysignf(float x, float y);
16       long double copysignl(long double x, long double y);
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18   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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20       copysign(), copysignf(), copysignl():
21           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
22               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
23               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

26       These  functions return a value whose absolute value matches that of x,
27       but whose sign bit matches that of y.
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29       For example, copysign(42.0, -1.0) and copysign(-42.0, -1.0) both return
30       -42.0.
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RETURN VALUE

33       On  success,  these  functions  return a value whose magnitude is taken
34       from x and whose sign is taken from y.
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36       If x is a NaN, a NaN with the sign bit of y is returned.
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ERRORS

39       No errors occur.
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ATTRIBUTES

42       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
43       tributes(7).
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45       ┌────────────────────────────────────────────┬───────────────┬─────────┐
46       │Interface                                   │ Attribute     │ Value   │
47       ├────────────────────────────────────────────┼───────────────┼─────────┤
48       │copysign(), copysignf(), copysignl()        │ Thread safety │ MT-Safe │
49       └────────────────────────────────────────────┴───────────────┴─────────┘
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VERSIONS

52       On  architectures  where  the  floating-point  formats are not IEEE 754
53       compliant, these functions may treat a negative zero as positive.
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STANDARDS

56       C11, POSIX.1-2008.
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58       This function is defined in IEC 559 (and the appendix with  recommended
59       functions in IEEE 754/IEEE 854).
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HISTORY

62       C99, POSIX.1-2001, 4.3BSD.
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