copysign, copysignf, copysignl - copy sign of a number
#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)):
These functions return a value whose absolute value matches that of
x, but whose sign bit matches that of
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
x and whose sign is taken from
x is a NaN, a NaN with the sign bit of
No errors occur.
C99, POSIX.1-2001, POSIX.1-2008. 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, these functions may treat a negative zero as positive.
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