copysign(3) Library Functions Manual copysign(3) copysign, copysignf, copysignl - (libm -lm) #include double copysign(double x, double y); float copysignf(float x, float y); long double copysignl(long double x, long double y); glibc ( feature_test_macros(7)): copysign(), copysignf(), copysignl(): _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE x y. copysign(42.0, -1.0) copysign(-42.0, -1.0) -42.0. x y. x NaN NaN y. . attributes(7). +------------+------------------------------------+--------------------+ || | | +------------+------------------------------------+--------------------+ |copysign(), | | MT-Safe | |copysignf(),| | | |copysignl() | | | +------------+------------------------------------+--------------------+ IEEE 754 . C11, POSIX.1-2008. IEC 559 ( IEEE 754/IEEE 854). C99 POSIX.1-2001 4.3BSD. signbit(3) 3 . . : . 6.18 8 2026 copysign(3)