rint, rintf, rintl, lrint, lrintf, lrintl, llrint, llrintf, llrintl
Defined in header <math.h>


float rintf( float arg ); 
(1)  (since C99) 
double rint( double arg ); 
(2)  (since C99) 
long double rintl( long double arg ); 
(3)  (since C99) 
Defined in header <tgmath.h>


#define rint( arg ) 
(4)  (since C99) 
Defined in header <math.h>


long lrintf( float arg ); 
(5)  (since C99) 
long lrint( double arg ); 
(6)  (since C99) 
long lrintl( long double arg ); 
(7)  (since C99) 
Defined in header <tgmath.h>


#define lrint( arg ) 
(8)  (since C99) 
Defined in header <math.h>


long long llrintf( float arg ); 
(9)  (since C99) 
long long llrint( double arg ); 
(10)  (since C99) 
long long llrintl( long double arg ); 
(11)  (since C99) 
Defined in header <tgmath.h>


#define llrint( arg ) 
(12)  (since C99) 
arg
to an integer value in floatingpoint format, using the current rounding mode.arg
to an integer value in integer format, using the current rounding mode.arg
has type long double, rintl
, lrintl
, llrintl
is called. Otherwise, if arg
has integer type or the type double, rint
, lrint
, llrint
is called. Otherwise, rintf
, lrintf
, llrintf
is called, respectively.Contents 
[edit] Parameters
arg    floating point value 
[edit] Return value
If no errors occur, the nearest integer value to arg
, according to the current rounding mode, is returned.
[edit] Error handling
Errors are reported as specified in math_errhandling
If the result of lrint
or llrint
is outside the range representable by the return type, a domain error or a range error may occur.
If the implementation supports IEEE floatingpoint arithmetic (IEC 60559),
 For the
rint
function:
 If
arg
is ±∞, it is returned, unmodified  If
arg
is ±0, it is returned, unmodified  If
arg
is NaN, NaN is returned
 For
lrint
andllrint
functions:
 If
arg
is ±∞, FE_INVALID is raised and an implementationdefined value is returned  If the result of the rounding is outside the range of the return type, FE_INVALID is raised and an implementationdefined value is returned
 If
arg
is NaN, FE_INVALID is raised and an implementationdefined value is returned
[edit] Notes
POSIX specifies that all cases where lrint
or llrint
raise FE_INEXACT are domain errors.
As specified in math_errhandling, FE_INEXACT may be (but isn't required to be on nonIEEE floatingpoint platforms) raised by rint
when rounding a noninteger finite value.
The only difference between rint
and nearbyint is that nearbyint never raises FE_INEXACT.
The largest representable floatingpoint values are exact integers in all standard floatingpoint formats, so rint
never overflows on its own; however the result may overflow any integer type (including intmax_t), when stored in an integer variable.
If the current rounding mode is...
 FE_DOWNWARD, then
rint
is equivalent to floor.  FE_UPWARD, then
rint
is equivalent to ceil.  FE_TOWARDZERO, then
rint
is equivalent to trunc  FE_TONEAREST, then
rint
differs from round in that halfway cases are rounded to even rather than away from zero.
[edit] Example
#include <stdio.h> #include <math.h> #include <fenv.h> #include <limits.h> int main(void) { #pragma STDC FENV_ACCESS ON fesetround(FE_TONEAREST); printf("rounding to nearest:\nrint(+2.3) = %+.1f ", rint(2.3)); printf("rint(+2.5) = %+.1f ", rint(2.5)); printf("rint(+3.5) = %+.1f\n", rint(3.5)); printf("rint(2.3) = %+.1f ", rint(2.3)); printf("rint(2.5) = %+.1f ", rint(2.5)); printf("rint(3.5) = %+.1f\n", rint(3.5)); fesetround(FE_DOWNWARD); printf("rounding down: \nrint(+2.3) = %+.1f ", rint(2.3)); printf("rint(+2.5) = %+.1f ", rint(2.5)); printf("rint(+3.5) = %+.1f\n", rint(3.5)); printf("rint(2.3) = %+.1f ", rint(2.3)); printf("rint(2.5) = %+.1f ", rint(2.5)); printf("rint(3.5) = %+.1f\n", rint(3.5)); printf("rounding down with lrint: \nlrint(+2.3) = %ld ", lrint(2.3)); printf("lrint(+2.5) = %ld ", lrint(2.5)); printf("lrint(+3.5) = %ld\n", lrint(3.5)); printf("lrint(2.3) = %ld ", lrint(2.3)); printf("lrint(2.5) = %ld ", lrint(2.5)); printf("lrint(3.5) = %ld\n", lrint(3.5)); printf("lrint(0.0) = %ld\n", lrint(0.0)); printf("lrint(Inf) = %ld\n", lrint(INFINITY)); // FE_INVALID raised // error handling feclearexcept(FE_ALL_EXCEPT); printf("rint(1.1) = %.1f\n", rint(1.1)); if(fetestexcept(FE_INEXACT)) puts(" FE_INEXACT was raised"); feclearexcept(FE_ALL_EXCEPT); printf("lrint(LONG_MIN2048.0) = %ld\n", lrint(LONG_MIN2048.0)); if(fetestexcept(FE_INVALID)) puts(" FE_INVALID was raised"); }
Possible output:
rounding to nearest: rint(+2.3) = +2.0 rint(+2.5) = +2.0 rint(+3.5) = +4.0 rint(2.3) = 2.0 rint(2.5) = 2.0 rint(3.5) = 4.0 rounding down: rint(+2.3) = +2.0 rint(+2.5) = +2.0 rint(+3.5) = +3.0 rint(2.3) = 3.0 rint(2.5) = 3.0 rint(3.5) = 4.0 rounding down with lrint: lrint(+2.3) = 2 lrint(+2.5) = 2 lrint(+3.5) = 3 lrint(2.3) = 3 lrint(2.5) = 3 lrint(3.5) = 4 lrint(0.0) = 0 lrint(Inf) = 9223372036854775808 rint(1.1) = 1.0 FE_INEXACT was raised lrint(LONG_MIN2048.0) = 9223372036854775808 FE_INVALID was raised
[edit] See also
(C99)(C99)(C99) 
rounds to nearest integer not greater in magnitude than the given value (function) 
(C99)(C99)(C99) 
rounds to an integer using current rounding mode (function) 
(C99)(C99) 
gets or sets rounding direction (function) 
C++ documentation for rint
