copysign(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);

   Link with -lm.

   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 versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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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