Varianti

    std::log

    Da cppreference.com.

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    <tbody> </tbody>
    Elemento definito nell'header <cmath>
    float log( float arg );
    double log( double arg );
    long double log( long double arg );
    double log( Integral arg );
    		 (dal C++11)

    Computes the natural (base e) logarithm of arg.

    Parametri

    arg -
    valore in virgola mobile
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    floating point value
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    Valore di ritorno

    natural logarithm of arg.

    Errore di dominio si verifica se arg è negativo. NAN viene restituito in questo caso.
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    Domain error occurs if arg is negative. NAN is returned in that case.
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    Campo errore si verifica se è arg 0. -HUGE_VAL viene restituito in questo caso.
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    Range error occurs if arg is 0. -HUGE_VAL is returned in that case.
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    Esempio

    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

    Vedi anche
    ritorna e elevato alla potenza data (ex)
    Original:
    returns e raised to the given power (ex)
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    (funzione) [modifica]
    calcola comune (base 10) logaritmo (log10(x))
    Original:
    computes common (base 10) logarithm (log10(x))
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    (funzione) [modifica]
    solleva un numero alla potenza data (xy)
    Original:
    raises a number to the given power (xy)
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    (funzione) [modifica]
    complesso logaritmo naturale con i rami di lungo l'asse reale negativo
    Original:
    complex natural logarithm with the branch cuts along the negative real axis
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    (funzione di modello) [modifica]
    applica la std::log funzione a ogni elemento di valarray
    Original:
    applies the function std::log to each element of valarray
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    (funzione di modello) [modifica]