std::logb

 

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Floating-point medio ambiente

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En tiempo de compilación aritmética racional (C++11)

Genéricos operaciones numéricas 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

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Funciones matemáticas comunes

Funciones Original: Functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
Operaciones básicas 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)
Funciones exponenciales 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)
Funciones de energía 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
Funciones trigonométricas e hiperbólicas 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)

Error gamma y funciones 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)
Más cerca de las operaciones con enteros en coma flotante 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)
Funciones de punto flotante de manipulación 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)
Clasificación / Comparación 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)
Constantes Macro 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)

 

Defined in header <cmath>
float       logb( float arg );		(desde C++11)
double      logb( double arg );		(desde C++11)
long double logb( long double arg );		(desde C++11)
double      logb( Integral arg );		(desde C++11)

Extrae el valor del exponente de la arg argumento de punto flotante, y la devuelve como un valor de punto flotante. Formalmente, el resultado es la parte integral de log
r|arg| como firmado valor de punto flotante, para no-cero arg, donde r es std::numeic_limits<T>::radix y T es el tipo de punto flotante de arg. Si arg es subnormal, es tratado como si se normalizó .

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.

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Parámetros

arg

-

flotando valor en puntos 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.

Valor de retorno

El exponente de punto flotante .

Original:

The floating-point exponent.

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Error de dominio o rango puede ocurrir si arg es cero .

Original:

Domain or range error may occur if arg is zero.

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Notas

El valor del exponente devuelto por std::logb siempre es 1 menos que el exponente reajustada por std::frexp debido a los requisitos de normalización diferentes: para la e exponente devuelto por std::logb, |arg*r-e
| es entre 1 y r (típicamente entre 1 y 2), pero para la exponente e devuelto por std::frexp, |arg*2-e
| es entre 0.5 y 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.

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Ejemplo

Compara las diferentes funciones de punto flotante de descomposición

Original:

Compares different floating-point decomposition functions

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#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';
}

Output:

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

Ver también

frexp	se descompone un número en mantisa y una potencia 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. (función)
ilogb (C++11)	extrae exponente de la serie 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. (función)
scalbn scalbln (C++11) (C++11)	multiplica un número por FLT_RADIX elevado a una potencia 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. (función)