COPYSIGN

 

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);

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 || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99

 

DESCRIPTION

The copysign(), copysignf(), and copysignl() 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

 

Multithreading (see pthreads(7))

The copysign(), copysignf(), and copysignl() functions are thread-safe.  

CONFORMING TO

C99, POSIX.1-2001. 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.