Linux manual pages Section 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);
 
[Note] Note
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
[Note] Note

Link with −lm.

DESCRIPTION

These functions return a value whose absolute value matches that of x, 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 from y.

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
copysign(), copysignf(), copysignl() Thread safety MT-Safe

CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008. 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 compliant, these functions may treat a negative zero as positive.

SEE ALSO

signbit(3)

COLOPHON

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