nearbyint, nearbyintf, nearbyintl

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Program utilities
Variadic function support
Error handling
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Input/output support
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Concurrency support(C11)
Technical Specifications
Symbol index

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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)

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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 nearbyintf(float arg);	(1)	(since C99)
double nearbyint(double arg);	(2)	(since C99)
longdouble nearbyintl(longdouble arg);	(3)	(since C99)
Defined in header`<tgmath.h>`
#define nearbyint( arg )	(4)	(since C99)

1-3) Rounds the floating-point argumentarg to an integer value in floating-point format, using thecurrent rounding mode.

4) Type-generic macro: Ifarg has typelongdouble,nearbyintl is called. Otherwise, ifarg has integer type or the typedouble,nearbyint is called. Otherwise,nearbyintf is called, respectively.

[edit]Parameters

arg

floating-point value

[edit]Return value

The nearest integer value toarg, according to thecurrent rounding mode, 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]Notes

The only difference betweennearbyint andrint is thatnearbyint never raisesFE_INEXACT.

The largest representable floating-point values are exact integers in all standard floating-point formats, sonearbyint never overflows on its own; however the result may overflow any integer type (includingintmax_t), when stored in an integer variable.

If the current rounding mode isFE_TONEAREST, this function rounds to even in halfway cases (likerint, but unlikeround).

[edit]Example

Run this code

#include <fenv.h>#include <math.h>#include <stdio.h> int main(void){// #pragma STDC FENV_ACCESS ONfesetround(FE_TONEAREST);printf("rounding to nearest:\nnearbyint(+2.3) = %+.1f  ", nearbyint(2.3));printf("nearbyint(+2.5) = %+.1f  ", nearbyint(2.5));printf("nearbyint(+3.5) = %+.1f\n", nearbyint(3.5));printf("nearbyint(-2.3) = %+.1f  ", nearbyint(-2.3));printf("nearbyint(-2.5) = %+.1f  ", nearbyint(-2.5));printf("nearbyint(-3.5) = %+.1f\n", nearbyint(-3.5)); fesetround(FE_DOWNWARD);printf("rounding down:\nnearbyint(+2.3) = %+.1f  ", nearbyint(2.3));printf("nearbyint(+2.5) = %+.1f  ", nearbyint(2.5));printf("nearbyint(+3.5) = %+.1f\n", nearbyint(3.5));printf("nearbyint(-2.3) = %+.1f  ", nearbyint(-2.3));printf("nearbyint(-2.5) = %+.1f  ", nearbyint(-2.5));printf("nearbyint(-3.5) = %+.1f\n", nearbyint(-3.5)); printf("nearbyint(-0.0) = %+.1f\n", nearbyint(-0.0));printf("nearbyint(-Inf) = %+.1f\n", nearbyint(-INFINITY));}

Output:

rounding to nearest:nearbyint(+2.3) = +2.0  nearbyint(+2.5) = +2.0  nearbyint(+3.5) = +4.0nearbyint(-2.3) = -2.0  nearbyint(-2.5) = -2.0  nearbyint(-3.5) = -4.0rounding down:nearbyint(+2.3) = +2.0  nearbyint(+2.5) = +2.0  nearbyint(+3.5) = +3.0nearbyint(-2.3) = -3.0  nearbyint(-2.5) = -3.0  nearbyint(-3.5) = -4.0nearbyint(-0.0) = -0.0nearbyint(-Inf) = -inf

[edit]References

C23 standard (ISO/IEC 9899:2024):

7.12.9.3 The nearbyint functions (p: TBD)

7.25 Type-generic math <tgmath.h> (p: TBD)

F.10.6.3 The nearbyint functions (p: TBD)

C17 standard (ISO/IEC 9899:2018):

7.12.9.3 The nearbyint functions (p: TBD)

7.25 Type-generic math <tgmath.h> (p: TBD)

F.10.6.3 The nearbyint functions (p: TBD)

C11 standard (ISO/IEC 9899:2011):

7.12.9.3 The nearbyint functions (p: 251-252)

7.25 Type-generic math <tgmath.h> (p: 373-375)

F.10.6.3 The nearbyint functions (p: 526)

C99 standard (ISO/IEC 9899:1999):

7.12.9.3 The nearbyint functions (p: 232)

7.22 Type-generic math <tgmath.h> (p: 335-337)

F.9.6.3 The nearbyint functions (p: 463)

[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]
fegetroundfesetround (C99)(C99)	gets or sets rounding direction (function)[edit]
C++ documentation fornearbyint