# roundeven, roundevenf, roundevenl

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< c‎ | numeric‎ | math

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

Run this code

    #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)

### See also

rint rintf rintl lrint lrintf lrintl llrint llrintf llrintl (C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99) | rounds to an integer using current rounding mode with exception if the result differs (function)
round roundf roundl lround lroundf lroundl llround llroundf llroundl (C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99) | rounds to nearest integer, rounding away from zero in halfway cases (function)

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