roundeven, roundevenf, roundevenl

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Headers
Type support
Program utilities
Variadic function support
Error handling
Dynamic memory management
Strings library
Algorithms
Numerics
Date and time utilities
Input/output support
Localization support
Concurrency support(C11)
Technical Specifications
Symbol index

[edit]

Numerics

Common mathematical functions
Floating-point environment(C99)
Pseudo-random number generation
Complex number arithmetic(C99)
Type-generic math(C99)
Bit manipulation(C23)
Checked integer arithmetic(C23)

[edit]

Common mathematical functions

Functions

Basic operations

abslabsllabsimaxabs (C99)(C99)
fabs
divldivlldivimaxdiv (C99)(C99)

fmod
remainder (C99)
remquo (C99)
fma (C99)
fdim (C99)
nannanfnanlnandN (C99)(C99)(C99)(C23)

Maximum/minimum operations

fmax (C99)
fmin (C99)
fmaximum (C23)
fminimum (C23)
fmaximum_mag (C23)

fmaximum_num (C23)
fminimum_mag (C23)
fminimum_num (C23)
fmaximum_mag_num (C23)
fminimum_mag_num (C23)

Exponential functions

exp
exp10 (C23)
exp2 (C99)
expm1 (C99)
exp10m1 (C23)
exp2m1 (C23)

log
log10
log2 (C99)
log1plogp1 (C99)(C23)
log10p1 (C23)
log2p1 (C23)

Power functions

sqrt
cbrt (C99)
rootn (C23)
rsqrt (C23)

hypot (C99)
compound (C23)
pow
pown (C23)
powr (C23)

Trigonometric and hyperbolic functions

sin
cos
tan
asin
acos
atan
atan2
sinpi (C23)
cospi (C23)
tanpi (C23)

asinpi (C23)
acospi (C23)
atanpi (C23)
atan2pi (C23)
sinh
cosh
tanh
asinh (C99)
acosh (C99)
atanh (C99)

Nearest integer floating-point

ceil
floor
roundlroundllround (C99)(C99)(C99)
roundeven (C23)
trunc (C99)

nearbyint (C99)
rintlrintllrint (C99)(C99)(C99)
fromfpfromfpxufromfpufromfpx (C23)(C23)(C23)(C23)

Floating-point manipulation

ldexp
frexp
scalbnscalbln (C99)(C99)
ilogbllogb (C99)(C23)
logb (C99)

modf
nextafternexttoward (C99)(C99)
nextupnextdown (C23)(C23)
copysign (C99)
canonicalize (C23)

Narrowing operations

fadd (C23)
fsub (C23)
fmul (C23)

fdiv (C23)
ffma (C23)
fsqrt (C23)

Quantum and quantum exponent

quantizedN (C23)
quantumdN (C23)

samequantumdN (C23)
llquantexpdN (C23)

Decimal re-encoding functions

encodedecdN (C23)
decodedecdN (C23)

encodebindN (C23)
decodebindN (C23)

Total order and payload functions

totalorder (C23)
getpayload (C23)

setpayload (C23)
setpayloadsig (C23)

Classification

fpclassify (C99)
iscanonical (C23)
isfinite (C99)
isinf (C99)
isnan (C99)
isnormal (C99)
signbit (C99)
issubnormal (C23)
iszero (C23)

isgreater (C99)
isgreaterequal (C99)
isless (C99)
islessequal (C99)
islessgreater (C99)
isunordered (C99)
issignaling (C23)
iseqsig (C23)

Error and gamma functions

erf (C99)
erfc (C99)

lgamma (C99)
tgamma (C99)

Types

div_tldiv_tlldiv_timaxdiv_t

(C99)(C99)

float_tdouble_t (C99)(C99)
_Decimal32_t_Decimal64_t (C23)(C23)

Macro constants

Special floating-point values

HUGE_VALHUGE_VALFHUGE_VALLHUGE_VALDN

(C99)(C99)(C23)

INFINITYDEC_INFINITY (C99)(C23)
NANDEC_NAN (C99)(C23)

Arguments and return values

FP_ILOGB0FP_ILOGBNAN (C99)(C99)
FP_NORMALFP_SUBNORMALFP_ZEROFP_INFINITEFP_NAN (C99)(C99)(C99)(C99)(C99)

FP_LLOGB0FP_LLOGBNAN (C23)(C23)
FP_INT_UPWARDFP_INT_DOWNWARDFP_INT_TOWARDZEROFP_INT_TONEARESTFROMZEROFP_INT_TONEAREST (C23)(C23)(C23)(C23)(C23)

Error handling

MATH_ERRNOMATH_ERRNOEXCEPT

(C99)(C99)

math_errhandling (C99)

Fast operation indicators

FP_FAST_FMAFFP_FAST_FMA (C99)(C99)
FP_FAST_FADDFP_FAST_FADDLFP_FAST_DADDLFP_FAST_DMADDDN (C23)(C23)(C23)(C23)
FP_FAST_FMULFP_FAST_FMULLFP_FAST_DMULLFP_FAST_DMMULDN (C23)(C23)(C23)(C23)
FP_FAST_FFMAFP_FAST_FFMALFP_FAST_DFMALFP_FAST_DMFMADN (C23)(C23)(C23)(C23)

FP_FAST_FMALFP_FAST_FMADN (C99)(C23)
FP_FAST_FSUBFP_FAST_FSUBLFP_FAST_DSUBLFP_FAST_DMSUBDN (C23)(C23)(C23)(C23)
FP_FAST_FDIVFP_FAST_FDIVLFP_FAST_DDIVLFP_FAST_DMDIVDN (C23)(C23)(C23)(C23)
FP_FAST_FSQRTFP_FAST_FSQRTLFP_FAST_DSQRTLFP_FAST_DMSQRTDN (C23)(C23)(C23)(C23)

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Defined in header`<math.h>`
float roundevenf(float arg);	(1)	(since C23)
double roundeven(double arg);	(2)	(since C23)
longdouble roundevenl(longdouble arg);	(3)	(since C23)
Defined in header`<tgmath.h>`
#define roundeven( arg )	(4)	(since C23)

1-3) Computes the nearest integer value toarg (in floating-point format), rounding halfway cases to nearest even integer, regardless of the current rounding mode.

4) Type-generic macro: Ifarg has typelongdouble,roundevenl is called. Otherwise, ifarg has integer type or the typedouble,roundeven is called. Otherwise,roundevenf is called, respectively.

[edit]Parameters

arg

floating-point value

[edit]Return value

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

[edit]Error handling

This function is not subject to any of the errors specified inmath_errhandling.

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

FE_INEXACT is never raised.
Ifarg is ±∞, it is returned, unmodified.
Ifarg is ±0, it is returned, unmodified.
Ifarg is NaN, NaN is returned.

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

[edit]References

C23 standard (ISO/IEC 9899:2024):

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

rintrintfrintllrintlrintflrintlllrintllrintfllrintl (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]
roundroundfroundllroundlroundflroundlllroundllroundfllroundl (C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)	rounds to nearest integer, rounding away from zero in halfway cases (function)[edit]