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Varianti

std::log

Da cppreference.com.
< cpp‎ | numeric‎ | math

 
 
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Defined in 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.

Indice

[modifica] Parametri

arg -
valore in virgola mobile
Original:
floating point value
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[modifica] Valore di ritorno

natural logarithm of arg.

Errore di dominio si verifica se arg è negativo. NAN viene restituito in questo caso.
Original:
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.
Original:
Range error occurs if arg is 0. -HUGE_VAL is returned in that case.
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[modifica] 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

[modifica] Vedi anche

ritorna e elevato alla potenza data (ex)
Original:
returns e raised to the given power (ex)
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(funzione) [edit]
calcola comune (base 10) logaritmo (log10(x))
Original:
computes common (base 10) logarithm (log10(x))
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(funzione) [edit]
solleva un numero alla potenza data (xy)
Original:
raises a number to the given power (xy)
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(funzione) [edit]
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) [edit]
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) [edit]