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Действия

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

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C++
 
Numerics библиотеки
 
Общие математические функции
Функции
Original:
Functions
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Основные операции
Original:
Basic operations
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remainder(C++11)
remquo(C++11)
fma(C++11)
fmax(C++11)
fmin(C++11)
fdim(C++11)
nan
nanf
nanl		(C++11)
(C++11)
(C++11)
Экспоненциальной функции
Original:
Exponential functions
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exp
exp2(C++11)
expm1(C++11)
log
log10
log1p(C++11)
log2(C++11)
Мощность функций
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Power functions
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sqrt
cbrt(C++11)
hypot(C++11)
pow
Тригонометрические и гиперболические функции
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Trigonometric and hyperbolic functions
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sinh
cosh
tanh
asinh(C++11)
acosh(C++11)
atanh(C++11)
Ошибка и гамма-функции
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Error and gamma functions
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erf(C++11)
erfc(C++11)
lgamma(C++11)
tgamma(C++11)
Ближайшее целое число операций с плавающей точкой
Original:
Nearest integer floating point operations
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ceil
floor
round
lround
llround		(C++11)
(C++11)
(C++11)
trunc(C++11)
nearbyint(C++11)
rint
lrint
llrint		(C++11)
(C++11)
(C++11)
Плавающей точкой функции манипуляции
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Floating point manipulation functions
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ldexp
scalbn
scalbln		(C++11)
(C++11)
ilogb(C++11)
logb(C++11)
frexp
modf
nextafter
nexttoward		(C++11)
(C++11)
copysign(C++11)
Классификация / сравнения
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Classification/Comparison
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fpclassify(C++11)
isfinite(C++11)
isinf(C++11)
isnan(C++11)
isnormal(C++11)
signbit(C++11)
isgreater(C++11)
isgreaterequal(C++11)
isless(C++11)
islessequal(C++11)
islessgreater(C++11)
isunordered(C++11)
Макро констант
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Macro constants
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FP_NORMAL
FP_SUBNORMAL
FP_ZERO
FP_INFINITE
FP_NAN		(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
 
Заголовочный файл <cmath>
int rint( float arg );
 (начиная с C++11)
int rint( double arg );
 (начиная с C++11)
int rint( long double arg );
 (начиная с C++11)
int rint( Integral arg );
 (начиная с C++11)
long lrint( float arg );
 (начиная с C++11)
long lrint( double arg );
 (начиная с C++11)
long lrint( long double arg );
 (начиная с C++11)
long lrint( Integral arg );
 (начиная с C++11)
long long llrint( float arg );
 (начиная с C++11)
long long llrint( double arg );
 (начиная с C++11)
long long llrint( long double arg );
 (начиная с C++11)
long long llrint( Integral arg );
 (начиная с C++11)
Раундов с плавающей точкой arg аргумент в целое число в формате с плавающей точкой, используя текущий режим округления. Если результат отличается от arg (т. е. arg не целое число уже), с плавающей точкой исключения FE_INEXACT поднимается.
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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Содержание

[править] Параметры

arg -
плавающей точкой
Original:
floating point value
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[править] Возвращаемое значение

Целое результате округления arg
Original:
The integer result of rounding arg
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[править] Notes

Единственное различие между std::nearbyint и std::rint в том, что std::rint может поднять FE_INEXACT с плавающей точкой исключения, а std::nearbyint никогда не поднимает его.
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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[править] Пример

#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";
    }
}

Вывод: 

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

[править] См. также

(C++11)
Ближайшая целое число, используя текущий режим округления
Original:
nearest integer using current rounding mode
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(функция) [edit]
(C++11)
ближайшего целого числа не больше по величине, чем заданное значение
Original:
nearest integer not greater in magnitude than the given value
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(функция) [edit]
(C++11)
(C++11)
получает или задает направление округления
Original:
gets or sets rounding direction
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(функция) [edit]
Источник — «http://ru.cppreference.com/mwiki/index.php?title=cpp/numeric/math/rint&oldid=31060»