COPYSIGNSection: Linux Programmer's Manual (3)
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NAMEcopysign, 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);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
DESCRIPTIONThe copysign() functions return a value whose absolute value matches that of x, but whose sign bit matches that of y.
RETURN VALUEOn success, these functions return a value whose magnitude is taken from x and whose sign is taken from y.
ERRORSNo errors occur.
CONFORMING TOC99, POSIX.1-2001. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).
NOTESOn architectures where the floating-point formats are not IEEE 754 compliant, the copysign() functions may treat a negative zero as positive.
COLOPHONThis page is part of release 3.21 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/.