std::log

来自cppreference.com

This page has been machine-translated from the English version of the wiki using Google Translate.

The translation may contain errors and awkward wording. Hover over text to see the original version. You can help to fix errors and improve the translation. For instructions click here.

 
C++
 
Numerics的图书馆
常见的数学函数
浮点环境
复数
数字阵列
伪随机数生成
编译时合理的算法 （C++11）
通用的数值运算
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
 
常见的数学函数
功能
Original:
Functions
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
基本操作
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.
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）
指数函数
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）
电源的功能
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
三角函数和双曲功能
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.
sinh
cosh
tanh
asinh（C++11）
acosh（C++11）
atanh（C++11）
错误和伽玛功能
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）
最接近的整数，浮点运算
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）
浮点操作功能
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）
分类/比较
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）
宏常量
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）
 
Defined in header <cmath>
float       log( float arg );
double      log( double arg );
long double log( long double arg );
double      log( Integral arg );
 （因为C + +11）

Computes the natural (base e) logarithm of arg.

目录

[编辑] 参数

arg -
浮点值
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.

[编辑] 返回值

natural logarithm of arg.

域时会出现错误arg为负。 NAN是在这种情况下，返回.
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.
如果arg​0​范围发生错误。 -HUGE_VAL是在这种情况下，返回.
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.

[编辑] 为例

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';
}

Output: 

8

[编辑] 另请参阅
返回“E”提出的功率（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.

（功能） [edit]
常见的计算（基地“10”）对数（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.

（功能） [edit]
引起了一些给定的功率（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.

（功能） [edit]
沿负实轴的割线复杂的自然对数
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.

（函数模板） [edit]
std::logvalarray的每个元素的功能
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.

（函数模板） [edit]
来自“http://zh.cppreference.com/mwiki/index.php?title=cpp/numeric/math/log&oldid=28955”