Espaços nominais
Variantes
Acções

std::numeric_limits::epsilon

Da cppreference.com

 
 
Biblioteca de utilitários
Digite apoio (basic types, RTTI, type traits)
Gerenciamento de memória dinâmica
De tratamento de erros
Utilidades do programa
Variadic funções
Data e hora
Objetos de função
initializer_list(C++11)
bitset
hash(C++11)
Os operadores relacionais
Original:
Relational operators
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
Pares e tuplas
Original:
Pairs and tuples
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
pair
tuple(C++11)
piecewise_construct_t(C++11)
piecewise_construct(C++11)
Troque, avançar e avançar
Original:
Swap, forward and move
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
swap
forward(C++11)
move(C++11)
move_if_noexcept(C++11)
declval(C++11)
 
Digite apoio
Tipos básicos
Original:
Basic types
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Tipos fundamentais
Tipos inteiros de largura fixos (C++11)
Limites numéricos
Original:
Numeric limits
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
numeric_limits
C numérico limita interface
Informações de tipo de tempo de execução
Original:
Runtime type information
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Características de tipo
Original:
Type traits
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
Principais categorias de tipo
Original:
Primary type categories
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
is_void(C++11)
is_array(C++11)
is_pointer(C++11)
is_enum(C++11)
is_union(C++11)
is_class(C++11)
is_function(C++11)
is_object(C++11)
is_scalar(C++11)
is_compound(C++11)
is_integral(C++11)
is_floating_point(C++11)
is_fundamental(C++11)
is_arithmetic(C++11)
is_reference(C++11)
is_lvalue_reference(C++11)
is_rvalue_reference(C++11)
is_member_pointer(C++11)
is_member_object_pointer(C++11)
is_member_function_pointer(C++11)
Propriedades de tipo
Original:
Type properties
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
is_const(C++11)
is_volatile(C++11)
is_pod(C++11)
is_empty(C++11)
is_polymorphic(C++11)
is_abstract(C++11)
Operações apoiadas
Original:
Supported operations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
is_constructible
is_trivially_constructible
is_nothrow_constructible
(C++11)
(C++11)
(C++11)
is_default_constructible
is_trivially_default_constructible
is_nothrow_default_constructible
(C++11)
(C++11)
(C++11)
is_copy_constructible
is_trivially_copy_constructible
is_nothrow_copy_constructible
(C++11)
(C++11)
(C++11)
is_move_constructible
is_trivially_move_constructible
is_nothrow_move_constructible
(C++11)
(C++11)
(C++11)
is_assignable
is_trivially_assignable
is_nothrow_assignable
(C++11)
(C++11)
(C++11)
is_copy_assignable
is_trivially_copy_assignable
is_nothrow_copy_assignable
(C++11)
(C++11)
(C++11)
is_move_assignable
is_trivially_move_assignable
is_nothrow_move_assignable
(C++11)
(C++11)
(C++11)
is_destructible
is_trivially_destructible
is_nothrow_destructible
(C++11)
(C++11)
(C++11)
has_virtual_destructor(C++11)
Relacionamentos e consultas de propriedade
Original:
Relationships and property queries
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
is_same(C++11)
is_base_of(C++11)
is_convertible(C++11)
alignment_of(C++11)
rank(C++11)
extent(C++11)
Tipo modificações
Original:
Type modifications
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
remove_cv
remove_const
remove_volatile
(C++11)
(C++11)
(C++11)
add_cv
add_const
add_volatile
(C++11)
(C++11)
(C++11)
make_signed(C++11)
make_unsigned(C++11)
Transformações tipo
Original:
Type transformations
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
aligned_storage(C++11)
aligned_union(C++11)
decay(C++11)
enable_if(C++11)
conditional(C++11)
common_type(C++11)
underlying_type(C++11)
result_of(C++11)
Digite constantes traço
Original:
Type trait constants
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
integral_constant(C++11)
 
std::numeric_limits
 
static T epsilon()
(até C + 11)
static constexpr T epsilon()
(a partir do C++ 11)
Retorna a epsilon máquina, isto é, a diferença entre 1.0 e o próximo valor representável pela T tipo de ponto flutuante. Ela só faz sentido se std::numeric_limits<T>::is_integer == false.
Original:
Returns the machine epsilon, that is, the difference between 1.0 and the next value representable by the floating-point type T. It is only meaningful if std::numeric_limits<T>::is_integer == false.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Índice

[editar] Valor de retorno

T std::numeric_limits<T>::epsilon()
/* non-specialized */ T();
bool false
char 0
signed char 0
unsigned char 0
wchar_t 0
char16_t 0
char32_t 0
short 0
unsigned short 0
int 0
unsigned int 0
long 0
unsigned long 0
long long 0
unsigned long long 0
float FLT_EPSILON
double DBL_EPSILON
long double LDBL_EPSILON

[editar] Exceções

noexcept specification:  
noexcept
  (a partir do C++ 11)

[editar] Exemplo

Demonstra o uso simplista de epsilon máquina para comparar valores de ponto flutuante .
Original:
Demonstrates the simplistic use of machine epsilon to compare floating-point values.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

#include <cmath>
#include <limits>
#include <iomanip>
#include <iostream>
#include <type_traits>
 
template<class T>
typename std::enable_if<!std::numeric_limits<T>::is_integer, bool>::type
    almost_equal(T x, T y, int ulp)
{
    // the machine epsilon has to be scaled to the magnitude of the larger value
    // and multiplied by the desired precision in ULPs (units in the last place)
    return std::abs(x-y) <=   std::numeric_limits<T>::epsilon()
                            * std::max(std::abs(x), std::abs(y))
                            * ulp;
}
int main()
{
    double d1 = 0.2;
    double d2 = 1 / std::sqrt(5) / std::sqrt(5);
 
    if(d1 == d2)
            std::cout << "d1 == d2\n";
    else
            std::cout << "d1 != d2\n";
 
    if(almost_equal(d1, d2, 2))
            std::cout << "d1 almost equals d2\n";
    else
            std::cout << "d1 does not almost equal d2\n";
}

Output:

d1 != d2
d1 almost equals d2

[editar] Veja também

(C++11)
(C++11)
valor próximo ponto flutuante representável para o valor fornecido
Original:
next representable floating point value towards the given value
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

(função) [edit]