/C

# copysign, copysignf, copysignl

Defined in header `<math.h>`
`float       copysignf( float x, float y );`
(1) (since C99)
`double      copysign( double x, double y );`
(2) (since C99)
`long double copysignl( long double x, long double y );`
(3) (since C99)
Defined in header `<tgmath.h>`
`#define copysign(x, y)`
(4) (since C99)
1-3) Composes a floating point value with the magnitude of `x` and the sign of `y`.
4) Type-generic macro: If any argument has type `long double`, `copysignl` is called. Otherwise, if any argument has integer type or has type `double`, `copysign` is called. Otherwise, `copysignf` is called.

### Parameters

 x, y - floating point values

### Return value

If no errors occur, the floating point value with the magnitude of `x` and the sign of `y` is returned.

If `x` is NaN, then NaN with the sign of `y` is returned.

If `y` is -0, the result is only negative if the implementation supports the signed zero consistently in arithmetic operations.

### Error handling

This function is not subject to any errors specified in math_errhandling.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

• The returned value is exact (`FE_INEXACT` is never raised) and independent of the current rounding mode.

### Notes

`copysign` is the only portable way to manipulate the sign of a NaN value (to examine the sign of a NaN, `signbit` may also be used).

### Example

```#include <stdio.h>
#include <math.h>

int main(void)
{
printf("copysign(1.0,+2.0)      = %+.1f\n", copysign(1.0,+2.0));
printf("copysign(1.0,-2.0)      = %+.1f\n", copysign(1.0,-2.0));
printf("copysign(INFINITY,-2.0) = %f\n",    copysign(INFINITY,-2.0));
printf("copysign(NAN,-2.0)      = %f\n",    copysign(NAN,-2.0));
}```

Possible output:

```copysign(1.0,+2.0)      = +1.0
copysign(1.0,-2.0)      = -1.0
copysign(INFINITY,-2.0) = -inf
copysign(NAN,-2.0)      = -nan```

### References

• C11 standard (ISO/IEC 9899:2011):
• 7.12.11.1 The copysign functions (p: 255)
• 7.25 Type-generic math <tgmath.h> (p: 373-375)
• F.10.8.1 The copysign functions (p: 529)
• C99 standard (ISO/IEC 9899:1999):
• 7.12.11.1 The copysign functions (p: 236)
• 7.22 Type-generic math <tgmath.h> (p: 335-337)
• F.9.8.1 The copysign functions (p: 465)

 fabsfabsffabsl (C99)(C99) computes absolute value of a floating-point value (\(\small{|x|}\)|x|) (function) signbit (C99) checks if the given number is negative (function macro) C++ documentation for `copysign`