copysign(3) - Linux manual page (original) (raw)

copysign(3) Library Functions Manual copysign(3)

NAME top

   copysign, copysignf, copysignl - copy sign of a number

LIBRARY top

   Math library (_libm_, _-lm_)

SYNOPSIS top

   **#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 top

   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 top

   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 top

   No errors occur.

ATTRIBUTES top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌──────────────────────────────────────┬───────────────┬─────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────────────────┼───────────────┼─────────┤
   │ **copysign**(), **copysignf**(), **copysignl**() │ Thread safety │ MT-Safe │
   └──────────────────────────────────────┴───────────────┴─────────┘

VERSIONS top

   On architectures where the floating-point formats are not IEEE 754
   compliant, these functions may treat a negative zero as positive.

STANDARDS top

   C11, POSIX.1-2008.

   This function is defined in IEC 559 (and the appendix with
   recommended functions in IEEE 754/IEEE 854).

HISTORY top

   C99, POSIX.1-2001, 4.3BSD.

SEE ALSO top

   [signbit(3)](../man3/signbit.3.html)

COLOPHON top

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Linux man-pages 6.10 2024-07-23 copysign(3)

Pages that refer to this page:signbit(3)