COPYSIGN(3) Linux Programmers Manual COPYSIGN(3)
copysign, copysignf, copysignl - copy sign of a number
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
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.
C99, 4.3BSD. 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 com
pliant, the copysign() functions may treat a negative zero as positive.
This page is part of release 3.05 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
GNU 2007-07-26 COPYSIGN(3)