Manpages - copysign.3

copysign, copysignf, copysignl - copy sign of a number

  #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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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.

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.

No errors occur.

For an explanation of the terms used in this section, see *attributes*(7).

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).

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

*signbit*(3)

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