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roundeven, roundevenf, roundevenl

From cppreference.com
< c‎ | numeric‎ | math
 
 
 
Common mathematical functions
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roundeven
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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.

Contents

[edit] Parameters

arg - floating-point value

[edit] Return value

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

[edit] 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.

[edit] 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

[edit] 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)

[edit] See also

(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)
rounds to an integer using current rounding mode with
exception if the result differs
(function) [edit]
(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)
rounds to nearest integer, rounding away from zero in halfway cases
(function) [edit]