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std::numeric_limits::round_style

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std::numeric_limits
 
static const std::float_round_style round_style
(até C + 11)
static constexpr std::float_round_style round_style
(a partir do C++ 11)
O valor de std::numeric_limits<T>::round_stylem identifica o estilo arredondamento usado pelo T tipo de ponto flutuante, sempre que um valor que não é um dos valores exactamente repesentable de T é armazenado em um objecto desse tipo.
Original:
The value of std::numeric_limits<T>::round_stylem identifies the rounding style used by the floating-point type T whenever a value that is not one of the exactly repesentable values of T is stored in an object of that type.
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[editar] Especializações padrão

T
valor de std::numeric_limits<T>::round_style
Original:
value of std::numeric_limits<T>::round_style
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/* non-specialized */ std::round_toward_zero
bool std::round_toward_zero
char std::round_toward_zero
signed char std::round_toward_zero
unsigned char std::round_toward_zero
wchar_t std::round_toward_zero
char16_t std::round_toward_zero
char32_t std::round_toward_zero
short std::round_toward_zero
unsigned short std::round_toward_zero
int std::round_toward_zero
unsigned int std::round_toward_zero
long std::round_toward_zero
unsigned long std::round_toward_zero
long long std::round_toward_zero
unsigned long long std::round_toward_zero
float
geralmente std::round_to_nearest
Original:
usually std::round_to_nearest
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double
geralmente std::round_to_nearest
Original:
usually std::round_to_nearest
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long double
geralmente std::round_to_nearest
Original:
usually std::round_to_nearest
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[editar] Exemplo

O valor decimal 0.1 não pode ser representado por um tipo de ponto flutuante binário. Quando armazenado em um IEEE-745 double, cai entre 0x1.9999999999999*2-4
e 0x1.999999999999a*2-4
. Arredondamento para o mais próximo valor resulta representáveis ​​em 0x1.999999999999a*2-4
.
Original:
The decimal value 0.1 cannot be represented by a binary floating-point type. When stored in an IEEE-745 double, it falls between 0x1.9999999999999*2-4
and 0x1.999999999999a*2-4
. Rounding to nearest representable value results in 0x1.999999999999a*2-4
.
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Do mesmo modo, o valor decimal de 0,3, o qual está entre 0x1.3333333333333*2-2
e 0x1.3333333333334*2-2
é arredondado para o mais próximo e é armazenada como 0x1.3333333333333*2-2
.
Original:
Similarly, the decimal value 0.3, which is between 0x1.3333333333333*2-2
and 0x1.3333333333334*2-2
is rounded to nearest and is stored as 0x1.3333333333333*2-2
.
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#include <iostream>
#include <limits>
int main()
{
    std::cout << std::hexfloat << "The decimal 0.1 is stored in a double as "
              << 0.1 << '\n'
              << "The decimal 0.3 is stored in a double as "
              << 0.3 << '\n'
              << "The rounding style is " << std::numeric_limits<double>::round_style << '\n';
}

Output:

The decimal 0.1 is stored in a double as 0x1.999999999999ap-4
The decimal 0.3 is stored in a double as 0x1.3333333333333p-2
The rounding style is 1

[editar] Veja também

indica os modos de ponto flutuante de arredondamento
Original:
indicates floating-point rounding modes
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(enum) [edit]