std::log

 

C++

Linguaggio

Concetti

Libreria di Utilità

Stringhe

Contenitori

Algoritmi

Iteratori

Libreria matematca

Input/output

Localizzazione

Espressioni regolari(C++11)

Operazioni atomicche(C++11)

Multithreading(C++11)

 

Numeri libreria

Comuni funzioni matematiche

Virgola mobile ambiente

I numeri complessi

Array numerici

Pseudo-casuale generazione

In fase di compilazione aritmetica razionale(C++11)

Generici operazioni numeriche 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

 

Comuni funzioni matematiche

Funzioni Original: Functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
Operazioni di base 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)
Funzioni esponenziali 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)
Funzioni di risparmio energia 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
Funzioni trigonometriche e iperboliche 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)

Errore e gamma funzioni 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)
Più vicini operazioni di interi in virgola mobile 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)
Floating funzioni di manipolazione di punti 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)
Classificazione / confronto 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)
Macro costanti 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)

 

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

Computes the natural (base e) logarithm of arg.

Parametri

arg

-

valore in virgola mobile 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.

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.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

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.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

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

exp	ritorna e elevato alla potenza data (ex) 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. (funzione)
log10	calcola comune (base 10) logaritmo (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. (funzione)
pow	solleva un numero alla potenza data (xy) 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. (funzione)
log(std::complex)	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 The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (funzione di modello)
log(std::valarray)	applica la std::log funzione a ogni elemento di valarray 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. (funzione di modello)