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COPYSIGN(3) Linux Programmer's Manual 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).

     allbox;  lbw36  lb  lb l l l.  Interface Attribute Value T{ copysign(),
     copysignf(), copysignl() T}   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 com-
     pliant, these functions may treat a negative zero as positive.