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definiert in Header <cmath>
float       log( float arg );
double      log( double arg );
long double log( long double arg );
double      log( Integral arg );
 (seit C++11)

Computes the natural (base e) logarithm of arg.

Inhaltsverzeichnis

[Bearbeiten] Parameter

arg -
Floating-Point-Wert
Original:
floating point value
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[Bearbeiten] Rückgabewert

natural logarithm of arg.

Domain-Fehler tritt auf, wenn arg negativ ist. NAN wird in diesem Fall wieder .
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Domain error occurs if arg is negative. NAN is returned in that case.
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Bereichs-Fehler tritt auf, wenn arg ist ​0​. -HUGE_VAL wird in diesem Fall wieder .
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Range error occurs if arg is ​0​. -HUGE_VAL is returned in that case.
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[Bearbeiten] Beispiel

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

[Bearbeiten] Siehe auch
Renditen e an die angegebene Leistung (ex) angehoben
Original:
returns e raised to the given power (ex)
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(Funktion) [edit]
berechnet gemeinsamen (base 10) Logarithmus (log10(x))
Original:
computes common (base 10) logarithm (log10(x))
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(Funktion) [edit]
wirft eine Reihe an die angegebene Leistung (xy)
Original:
raises a number to the given power (xy)
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(Funktion) [edit]
komplexen natürlichen Logarithmus mit den Niederlassungen Schnitte entlang der negativen reellen Achse
Original:
complex natural logarithm with the branch cuts along the negative real axis
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(Funktions-Template) [edit]
wendet die Funktion std::log auf jedes Element valarray
Original:
applies the function std::log to each element of valarray
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(Funktions-Template) [edit]
Von „https://de.cppreference.com/mwiki/index.php?title=cpp/numeric/math/log&oldid=29597“