Namespace
Varianti

std::log

Da cppreference.com.
< cpp‎ | numeric‎ | math

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C++
 
Numeri libreria
Comuni funzioni matematiche
Virgola mobile ambiente
I numeri complessi
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Pseudo-casuale generazione
In fase di compilazione aritmetica razionale (C++11)
Generici operazioni numeriche
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Generic numeric operations
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iota(C++11)
accumulate
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Comuni funzioni matematiche
Funzioni
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Functions
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Operazioni di base
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Basic operations
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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)
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Funzioni esponenziali
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Exponential functions
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exp
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expm1(C++11)
log
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Macro costanti
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FP_NORMAL
FP_SUBNORMAL
FP_ZERO
FP_INFINITE
FP_NAN		(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
 
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.

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.
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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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[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) [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]
Estratto da "https://it.cppreference.com/mwiki/index.php?title=cpp/numeric/math/log&oldid=26294"