std::rint, std::lrint, std::llrint – cppreference.com

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definiert in Header `<cmath>`

`int rint( float arg );`		(seit C++11)

`int rint( double arg );`		(seit C++11)

`int rint( long double arg );`		(seit C++11)

`int rint( Integral arg );`		(seit C++11)

`long lrint( float arg );`		(seit C++11)

`long lrint( double arg );`		(seit C++11)

`long lrint( long double arg );`		(seit C++11)

`long lrint( Integral arg );`		(seit C++11)

`long long llrint( float arg );`		(seit C++11)

`long long llrint( double arg );`		(seit C++11)

`long long llrint( long double arg );`		(seit C++11)

`long long llrint( Integral arg );`		(seit C++11)

Rundet die Floating-Point-Argument arg auf einen ganzzahligen Wert in Floating-Point-Format, mit dem aktuellen Rundung Modus. Wenn das Ergebnis unterscheidet sich von arg (dh arg war kein ganzzahliger Wert schon), wird die Gleitkomma-Ausnahme FE_INEXACT angehoben .

Original:

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.

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Parameter

arg

Floating-Point-Wert

Original:

floating point value

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Rückgabewert

Das ganzzahlige Ergebnis der Rundung arg

Original:

The integer result of rounding arg

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Notes

Der einzige Unterschied zwischen std::nearbyint und std::rint ist, dass std::rint kann die FE_INEXACT Gleitkomma-Ausnahme zu erhöhen, während std::nearbyint wirft es nie .

Original:

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.

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Beispiel

#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

Siehe auch


nearbyint (C++11)	nächste ganze Zahl mit aktuellen Rundung Modus Original: nearest integer using current rounding mode The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Funktion) [edit]

trunc (C++11)	nächste Ganzzahl nicht betragsmäßig größer als der gegebene Wert Original: nearest integer not greater in magnitude than the given value The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Funktion) [edit]

fegetround fesetround (C++11) (C++11)	ab oder legt Rundung Richtung Original: gets or sets rounding direction The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Funktion) [edit]