std::log

 

C++

言語

コンセプト

ユーティリティライブラリ

ストリングスライブラリ

コンテナライブラリ

アルゴリズムライブラリ

イテレータライブラリ

ニューメリックスライブラリ

入力/出力ライブラリ

ローカライゼーションライブラリ

正規表現ライブラリ (C++11)

アトミック操作ライブラリ (C++11)

スレッドのサポートライブラリ (C++11)

 

ニューメリックスライブラリ

一般的な数学関数

浮動小数点環境

複素数

数値配列

擬似乱数生成

コンパイル時有理数演算 (C++11)

汎用の数値演算 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

 

一般的な数学関数

機能します 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.
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)
指数関数 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)
電源機能 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
三角関数や双曲線関数 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)

エラーおよびガンマ関数 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)
最も近い整数の浮動小数点演算 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)
点操作関数に浮かぶ 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)
分類/比較 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)
マクロ定数 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 );		(C++11およびそれ以降)

Computes the natural (base e) logarithm of arg.

パラメータ

arg

-

浮動小数点値 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.

値を返します

natural logarithm of arg.

argが負の場合はドメイン·エラーが発生します。 NANはその場合に返されます.

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.

arg​0​場合、範囲エラーが発生します。 -HUGE_VALはその場合に返されます.

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.

例

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

このコードを実行します

#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';
}

出力:

8

も参照してください

exp	戻り eを与えられた電力（ex）に引き上げた 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. (関数)
log10	計算するコモン（ベース 10）対数（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. (関数)
pow	与えられた電力（xy）に番号を発生させます 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. (関数)
log(std::complex)	負の実軸に沿って分岐切断線を持つ複雑な自然対数 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. (関数テンプレート)
log(std::valarray)	valarrayの各要素に関数を適用しstd::log 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. (関数テンプレート)