Espaces de noms
Variantes
Affichages
Actions

std::logb

De cppreference.com
< cpp‎ | numeric‎ | math

This page has been machine-translated from the English version of the wiki using Google Translate.

The translation may contain errors and awkward wording. Hover over text to see the original version. You can help to fix errors and improve the translation. For instructions click here.

Click here for the English version of this page

 
C++
 
Bibliothèque Numerics
Fonctions mathématiques courantes
Virgule flottante environnement
Nombres complexes
Tableaux numériques
La génération de nombres pseudo-aléatoires
Moment de la compilation arithmétique rationnelle (C++11)
Génériques des opérations numériques
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
 
Fonctions mathématiques courantes
{{{1}}}
Original:
{{{2}}}
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Fonctions
Original:
Functions
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Opérations de 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.
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)
Les fonctions exponentielles
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)
Les fonctions de puissance
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
Les fonctions trigonométriques et hyperboliques
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.
sinh
cosh
tanh
asinh (C++11)
acosh (C++11)
atanh (C++11)
{{{1}}}
Original:
{{{2}}}
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Erreur fonctions et gamma
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)
Entier le plus proche opérations en virgule flottante
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)
Flottant fonctions de manipulation de points
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)
Classification / Comparaison
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 constantes
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.
FP_NORMAL
FP_SUBNORMAL
FP_ZERO
FP_INFINITE
FP_NAN		 (C++11)
(C++11)
(C++11)
(C++11)
(C++11)
</div>
 
</div>
Déclaré dans l'en-tête <cmath>
float       logb( float arg );
 (depuis C++11)
double      logb( double arg );
 (depuis C++11)
long double logb( long double arg );
 (depuis C++11)
double      logb( Integral arg );
 (depuis C++11)
Extrait la valeur de l'exposant de la arg argument en virgule flottante, et retourne une valeur à virgule flottante. Formellement, le résultat est la partie intégrante de log
r|arg| signé en tant que valeur à virgule flottante, pour les non-nul arg, où r est std::numeic_limits<T>::radix et T est le type à virgule flottante de arg. Si arg est inférieure à la normale, elle est traitée comme si elle était normalisée .
Original:
Extracts the value of the exponent from the floating-point argument arg, and returns it as a floating-point value. Formally, the result is the integral part of log
r|arg| as a signed floating-point value, for non-zero arg, where r is std::numeic_limits<T>::radix and T is the floating-point type of arg. If arg is subnormal, it is treated as though it was normalized.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Sommaire

[modifier] Paramètres

arg -
valeur du point flottant
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.

[modifier] Retourne la valeur

L'exposant virgule flottante .
Original:
The floating-point exponent.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Erreur de domaine ou une plage peut se produire si arg est nul .
Original:
Domain or range error may occur if arg is zero.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[modifier] Notes

La valeur de l'exposant retourné par std::logb est toujours inférieur de 1 l'exposant retuned par std::frexp en raison des exigences de normalisation différents: pour le e exposant retourné par std::logb, |arg*r-e
| est comprise entre 1 et r (typiquement entre 1 et 2), mais pour le exposant e retourné par std::frexp, |arg*2-e
| se situe entre 0.5 et 1 .
Original:
The value of the exponent returned by std::logb is always 1 less than the exponent retuned by std::frexp because of the different normalization requirements: for the exponent e returned by std::logb, |arg*r-e
| is between 1 and r (typically between 1 and 2), but for the exponent e returned by std::frexp, |arg*2-e
| is between 0.5 and 1.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

[modifier] Exemple

Compare les différentes fonctions de décomposition en virgule flottante
Original:
Compares different floating-point decomposition functions
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

#include <iostream>
#include <cmath>
#include <limits>
int main()
{
    double f = 123.45;
    std::cout << "Given the number " << f << " or " << std::hexfloat
              << f << std::defaultfloat << " in hex,\n";
 
    double f3;
    double f2 = std::modf(f, &f3);
    std::cout << "modf() makes " << f3 << " + " << f2 << '\n';
 
    int i;
    f2 = std::frexp(f, &i);
    std::cout << "frexp() makes " << f2 << " * 2^" << i << '\n';
 
    i = std::ilogb(f);
    std::cout << "logb()/ilogb() make " << f/std::scalbn(1.0, i) << " * "
              << std::numeric_limits<double>::radix
              << "^" << std::ilogb(f) << '\n';
}

Résultat : 

Given the number 123.45 or 0x1.edccccccccccdp+6 in hex,
modf() makes 123 + 0.45
frexp() makes 0.964453 * 2^7
logb()/ilogb() make 1.92891 * 2^6

[modifier] Voir aussi
se décompose en un certain nombre mantisse et d'une puissance de 2
Original:
decomposes a number into significand and a power of 2
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

(fonction) [edit]
(C++11)
extrait exposant du nombre
Original:
extracts exponent of the number
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

(fonction) [edit]
(C++11)
(C++11)
multiplie par un nombre FLT_RADIX élevé à une puissance
Original:
multiplies a number by FLT_RADIX raised to a power
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

(fonction) [edit]
Récupérée de « https://fr.cppreference.com/mwiki/index.php?title=cpp/numeric/math/logb&oldid=48863 »