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copysign (3)
COPYSIGN(3) Linux Programmer's Manual COPYSIGN(3)
NAME
copysign, copysignf, copysignl - copy sign of a number
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);
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; or cc -std=c99
DESCRIPTION
The copysign() functions return a value whose absolute value matches
that of x, but whose sign bit matches that of y. If x is a NaN, then a
NaN with the sign bit of y is returned.
CONFORMING TO
C99, 4.3BSD. This function is defined in IEC 559 (and the appendix
with recommended functions in IEEE 754/IEEE 854).
NOTES
On architectures where the floating-point formats are not IEEE 754 com-
pliant, the copysign() functions may treat a negative zero as positive.
SEE ALSO
signbit(3)
GNU 2007-07-26 COPYSIGN(3)
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