copysign(3) Library Functions Manual copysign(3)
NAME
copysign, copysignf, copysignl - copy sign of a number
LIBRARY
Math library (libm, -lm)
SYNOPSIS
#include <math.h>
double copysign(double x, double y);
float copysignf(float x, float y);
long double copysignl(long double x, long double y);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
copysign(), copysignf(), copysignl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
These functions return a value whose absolute value matches that of x,
but whose sign bit matches that of y.
For example, copysign(42.0, -1.0) and copysign(-42.0, -1.0) both return
-42.0.
RETURN VALUE
On success, these functions return a value whose magnitude is taken from
x and whose sign is taken from y.
If x is a NaN, a NaN with the sign bit of y is returned.
ERRORS
No errors occur.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│ copysign(), copysignf(), copysignl() │ Thread safety │ MT-Safe │
└────────────────────────────────────────────┴───────────────┴─────────┘
VERSIONS
On architectures where the floating-point formats are not IEEE 754 com-
pliant, these functions may treat a negative zero as positive.
STANDARDS
C11, POSIX.1-2008.
This function is defined in IEC 559 (and the appendix with recommended
functions in IEEE 754/IEEE 854).
HISTORY
C99, POSIX.1-2001, 4.3BSD.
SEE ALSO
signbit(3)
Linux man-pages 6.9.1 2024-05-02 copysign(3)
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