Name
copysign, copysignf, copysignl - copy sign of a numberLibrary
Math library ( libm ", " -lm )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 );
Feature Test Macro Requirements for glibc (see 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
Description
These functions return a value whose absolute value matches that ofx, but whose sign bit matches that of y. For example, "copysign(42.0,\ -1.0)" and "copysign(-42.0, -1.0)" both return -42.0.
Return Value
On success, these functions return a value whose magnitude is taken from x and whose sign is taken fromy. If x is a NaN, a NaN with the sign bit of y is returned.
Errors
No errors occur.Attributes
For an explanation of the terms used in this section, see attributes(7).| Interface | Attribute | Value |
| T} | Thread safety | MT-Safe |
Versions
On architectures where the floating-point formats are not IEEE 754 compliant, these functions may treat a negative zero as positive.Standards
C11, POSIX.1-2008.This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).
History
C99, POSIX.1-2001, 4.3BSD.See Also
- signbit(3)