/C

# roundeven, roundevenf, roundevenl

Defined in header `<math.h>`
`float       roundevenf( float arg );`
(1) (since C23)
`double      roundeven( double arg );`
(2) (since C23)
`long double roundevenl( long double arg );`
(3) (since C23)
Defined in header `<tgmath.h>`
`#define roundeven( arg )`
(4) (since C23)
1-3) Computes the nearest integer value to `arg` (in floating-point format), rounding halfway cases to nearest even integer, regardless of the current rounding mode.
4) Type-generic macro: If `arg` has type `long double`, `roundevenl` is called. Otherwise, if `arg` has integer type or the type `double`, `roundeven` is called. Otherwise, `roundevenf` is called, respectively.

### Parameters

 arg - floating point value

### Return value

If no errors occur, the nearest integer value to `arg`, rounding halfway cases to nearest even integer, is returned.

### Error handling

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

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

• `FE_INEXACT` is never raised
• If `arg` is ±∞, it is returned, unmodified
• If `arg` is ±0, it is returned, unmodified
• If `arg` is NaN, NaN is returned

### Example

```#include <math.h>
#include <stdio.h>
int main(void)
{
printf("roundeven(+2.4) = %+.1f\n", roundeven(2.4));
printf("roundeven(-2.4) = %+.1f\n", roundeven(-2.4));
printf("roundeven(+2.5) = %+.1f\n", roundeven(2.5));
printf("roundeven(-2.5) = %+.1f\n", roundeven(-2.5));
printf("roundeven(+2.6) = %+.1f\n", roundeven(2.6));
printf("roundeven(-2.6) = %+.1f\n", roundeven(-2.6));
printf("roundeven(+3.5) = %+.1f\n", roundeven(3.5));
printf("roundeven(-3.5) = %+.1f\n", roundeven(-3.5));
printf("roundeven(-0.0) = %+.1f\n", roundeven(-0.0));
printf("roundeven(-Inf) = %+f\n",   roundeven(-INFINITY));
}```

Possible output:

```roundeven(+2.4) = +2.0
roundeven(-2.4) = -2.0
roundeven(+2.5) = +2.0
roundeven(-2.5) = -2.0
roundeven(+2.6) = +3.0
roundeven(-2.6) = -3.0
roundeven(+3.5) = +4.0
roundeven(-3.5) = -4.0
roundeven(-0.0) = -0.0
roundeven(-Inf) = -inf```

### References

• C23 standard (ISO/IEC 9899:2023):
• 7.12.9.8 The roundeven functions (p: 265-266)
• 7.27 Type-generic math <tgmath.h> (p: 386-390)
• F.10.6.8 The roundeven functions (p: 532)