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# std::rint, std::lrint, std::llrint

From cppreference.com
< cpp‎ | numeric‎ | math

Defined in header `<cmath>` |  |
float rint( float arg ); |  | (since C++11)
double rint( double arg ); |  | (since C++11)
long double rint( long double arg ); |  | (since C++11)
double rint( Integral arg ); |  | (since C++11)
long lrint( float arg ); |  | (since C++11)
long lrint( double arg ); |  | (since C++11)
long lrint( long double arg ); |  | (since C++11)
long lrint( Integral arg ); |  | (since C++11)
long long llrint( float arg ); |  | (since C++11)
long long llrint( double arg ); |  | (since C++11)
long long llrint( long double arg ); |  | (since C++11)
long long llrint( Integral arg ); |  | (since C++11)

Rounds the floating-point argument `arg` to an integer value in floating-point format, using the current rounding mode. If the result differs from `arg` (i.e., `arg` was not an integer value already), the floating-point exception FE_INEXACT is raised.

### [edit] Parameters

arg | - | floating point value

### [edit] Return value

The integer result of rounding `arg`

### [edit] Notes

The only difference between std::nearbyint and std::rint is that std::rint may raise the FE_INEXACT floating-point exception, while std::nearbyint never raises it.

### [edit] Example

Run this code

    #include <cmath>
    #include <cfenv>
    #include <iostream>
    int main()
    {
        #pragma STDC FENV_ACCESS ON
        std::fesetround(FE_DOWNWARD);
        std::cout << "rounding using FE_DOWNWARD:\n" << std::fixed
                  << " 12.0 ->  " << std::rint(12.0) << '\n'
                  << " 12.1 ->  " << std::rint(12.1) << '\n'
                  << "-12.1 -> " << std::rint(-12.1) << '\n'
                  << " 12.5 ->  " << std::rint(12.5) << '\n'
                  << " 12.9 ->  " << std::rint(12.9) << '\n'
                  << "-12.9 -> " << std::rint(-12.9) << '\n'
                  << " 13.0 ->  " << std::rint(13.0) << '\n';
        std::fesetround(FE_TONEAREST);
        std::cout << "rounding using FE_TONEAREST: \n"
                  << " 12.0 ->  " << std::rint(12.0) << '\n'
                  << " 12.1 ->  " << std::rint(12.1) << '\n'
                  << "-12.1 -> " << std::rint(-12.1) << '\n'
                  << " 12.5 ->  " << std::rint(12.5) << '\n'
                  << " 12.9 ->  " << std::rint(12.9) << '\n'
                  << "-12.9 -> " << std::rint(-12.9) << '\n'
                  << " 13.0 ->  " << std::rint(13.0) << '\n';

        std::cout << "When rounding 12.0 ";
        std::feclearexcept(FE_ALL_EXCEPT);
        std::rint(12.0);
        if(std::fetestexcept(FE_ALL_EXCEPT) & FE_INEXACT) {
            std::cout << "inexact result reported\n";
        } else {
            std::cout << "inexact result not reported\n";
        }

        std::cout << "When rounding 12.1 ";
        std::rint(12.1);
        if(std::fetestexcept(FE_ALL_EXCEPT) & FE_INEXACT) {
            std::cout << "inexact result reported\n";
        } else {
            std::cout << "inexact result not reported\n";
        }
    }

Output:

    rounding using FE_DOWNWARD:
     12.0 ->  12.000000
     12.1 ->  12.000000
    -12.1 -> -13.000000
     12.5 ->  12.000000
     12.9 ->  12.000000
    -12.9 -> -13.000000
     13.0 ->  13.000000
    rounding using FE_TONEAREST:
     12.0 ->  12.000000
     12.1 ->  12.000000
    -12.1 -> -12.000000
     12.5 ->  12.000000
     12.9 ->  13.000000
    -12.9 -> -13.000000
     13.0 ->  13.000000
    When rounding 12.0 inexact result not reported
    When rounding 12.1 inexact result reported

### [edit] See also

nearbyint (C++11) | nearest integer using current rounding mode (function) [edit]
trunc (C++11) | nearest integer not greater in magnitude than the given value (function) [edit]
fegetround fesetround (C++11)(C++11) | gets or sets rounding direction (function) [edit]

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