std::log

 

C++

Язык

Понятия

Утилиты библиотеки

Струны библиотеки

Контейнеры библиотеки

Алгоритмы библиотеки

Итераторы библиотеки

Numerics библиотеки

Библиотеки ввода / вывода

Локализация библиотеки

Библиотеки регулярных выражений (C++11)

Атомная библиотеке операций (C++11)

Библиотека тему поддержки (C++11)

 

Numerics библиотеки

Общие математические функции

Плавающей точкой окружающей среды

Комплексные числа

Числовых массивов

Псевдослучайных чисел поколения

Во время компиляции рациональной арифметики (C++11)

Generic числовые операции Original: Generic numeric operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

iota (C++11)

accumulate

inner_product

adjacent_difference

partial_sum

 

Общие математические функции

Функции Original: Functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
Основные операции Original: Basic operations The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
abs(int) labs llabs imaxabs (C++11) abs(float) fabs div ldiv lldiv imaxdiv (C++11) fmod	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 The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
exp exp2 (C++11) expm1 (C++11)	log log10 log1p (C++11) log2 (C++11)
Мощность функций Original: Power functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
sqrt cbrt (C++11)	hypot (C++11) pow
Тригонометрические и гиперболические функции Original: Trigonometric and hyperbolic functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
sin cos tan asin acos atan atan2	sinh cosh tanh asinh (C++11) acosh (C++11) atanh (C++11)

Ошибка и гамма-функции Original: Error and gamma functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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 The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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 Original: Floating point manipulation functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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 Original: Classification/Comparison The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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 Original: Macro constants The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
HUGE_VALF HUGE_VAL HUGE_VALL (C++11) (C++11) INFINITY (C++11) NAN (C++11) math_errhandling MATH_ERRNO MATH_ERREXCEPT (C++11)	FP_NORMAL FP_SUBNORMAL FP_ZERO FP_INFINITE FP_NAN (C++11) (C++11) (C++11) (C++11) (C++11)

 

Заголовочный файл <cmath>
float       log( float arg );
double      log( double arg );
long double log( long double arg );
double      log( Integral arg );		(начиная с C++11)

Computes the natural (base e) logarithm of arg.

Параметры

arg

-

плавающей точкой Original: floating point value The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Возврат стоимости

natural logarithm of arg.

Домен ошибка возникает, если arg отрицательный. NAN возвращается в том случае.

Original:

Domain error occurs if arg is negative. NAN is returned in that case.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Диапазон ошибка возникает, если arg является ​0​. -HUGE_VAL возвращается в том случае.

Original:

Range error occurs if arg is ​0​. -HUGE_VAL is returned in that case.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Пример

The following code computes the binary (base 2) logarithm with help of natural logarithm.

#include <cmath>
#include <iostream>
 
int main()
{
    double base = 2.0;
    double arg  = 256.0;
    double result = std::log(arg) / std::log(base);
 
    std::cout << result << '\n';
}

Вывод:

8

См. также

exp	возвращает е поднял к данной мощности (ex) Original: returns e raised to the given power (ex) The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (функция)
log10	вычисляет общие (базовые 10) логарифм (log10(x)) Original: computes common (base 10) logarithm (log10(x)) The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (функция)
pow	возводит число в данном мощности (xy) Original: raises a number to the given power (xy) The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (функция)
log(std::complex)	Комплекс натуральный логарифм с разрезов вдоль отрицательной действительной оси Original: complex natural logarithm with the branch cuts along the negative real axis The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (шаблон функции)
log(std::valarray)	применяет функцию std::log к каждому элементу valarray Original: applies the function std::log to each element of valarray The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (шаблон функции)