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std::tuple_size<std::tuple>

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< cpp‎ | utility‎ | tuple

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C++
 
Utilità libreria
Tipo di supporto (basic types, RTTI, type traits)
Gestione della memoria dinamica
La gestione degli errori
Programma di utilità
Funzioni variadic
Data e ora
Funzione oggetti
initializer_list(C++11)
bitset
hash(C++11)
Gli operatori relazionali
Original:
Relational operators
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rel_ops::operator!=
rel_ops::operator>
rel_ops::operator<=
rel_ops::operator>=
Coppie e tuple
Original:
Pairs and tuples
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pair
tuple(C++11)
piecewise_construct_t(C++11)
piecewise_construct(C++11)
Swap, in avanti e spostare
Original:
Swap, forward and move
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swap
forward(C++11)
move(C++11)
move_if_noexcept(C++11)
declval(C++11)
 
std::tuple
Membri funzioni
Original:
Member functions
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tuple::tuple
tuple::operator=
tuple::swap
Non membri funzioni
Original:
Non-member functions
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make_tuple
tie
forward_as_tuple
None
operator=
operator!=
operator<
operator<=
operator>
operator>=
std::swap
get
Helper classi
Original:
Helper classes
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tuple_size
tuple_element
uses_allocator
ignore
 
Elemento definito nell'header <tuple>
template< class T >
class tuple_size; /*undefined*/
 (1) (dal C++11)
template< class... Types >

class tuple_size<tuple<Types...> >

 : public std::integral_constant<std::size_t, sizeof...(Types)> { };
 (2) (dal C++11)
template< class T >

class tuple_size<const T>
 : public std::integral_constant<
             typename std::remove_cv<decltype(std::tuple_size<T>::value)>::type,

             std::tuple_size<Tp>::value> { };
 (3) (dal C++11)
template< class T >

class tuple_size< volatile T >
 : public std::integral_constant<
             typename std::remove_cv<decltype(std::tuple_size<T>::value)>::type,

             std::tuple_size<Tp>::value> { };
 (4) (dal C++11)
template< class T >

class tuple_size< const volatile T >
 : public std::integral_constant<
             typename std::remove_cv<decltype(std::tuple_size<T>::value)>::type,

             std::tuple_size<Tp>::value> { };
 (5) (dal C++11)
Consente di accedere al numero di elementi in una tupla come un tempo di compilazione espressione costante.
Original:
Provides access to the number of elements in a tuple as a compile-time constant expression.
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Indice

Inherited from std::integral_constant

Member constants

value
[statico]
 sizeof...(Types)
(pubblico membro statico costante)

Member functions

operator std::size_t
converte l'oggetto in std::size_t, restituisce value
Original:
converts the object to std::size_t, returns value
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(metodo pubblico)

Member types

Tipo
Original:
Type
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 Definition
value_type std::size_t
type std::integral_constant<std::size_t, value>

[modifica] Esempio

#include <iostream>
#include <tuple>
 
template<class T>
void test(T t)
{
    int a[std::tuple_size<T>::value]; // can be used at compile time
    std::cout << std::tuple_size<T>::value << '\n'; // or at run time
}
 
int main()
{
    test(std::make_tuple(1, 2, 3.14));
}

Output: 

3

[modifica] Vedi anche
ottiene la dimensione di un array
Original:
obtains the size of an array
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(classe modello di specializzazione) [modifica]
(C++11)
ottiene la dimensione di un pair
Original:
obtains the size of a pair
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(classe modello di specializzazione) [modifica]
tupla accede elemento specificato
Original:
tuple accesses specified element
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(funzione di modello) [modifica]
ottiene il tipo dell'elemento specificato
Original:
obtains the type of the specified element
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(classe modello di specializzazione) [modifica]
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