copysign, copysignf, copysignl − copy sign of a number
copysign(double x, double y);
float copysignf(float x, float y);
long double copysignl(long double x, long double y);
Link with −lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
copysign(), copysignf(), copysignl():
_SVID_SOURCE || _BSD_SOURCE ||
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
The copysign() 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.
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.
No errors occur.
For an explanation of the terms used in this section, see attributes(7).
C99, POSIX.1-2001. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).
On architectures where the floating-point formats are not IEEE 754 compliant, the copysign() functions may treat a negative zero as positive.
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