std::vector::front

<metanoindex/>

 

C++

Linguaggio

Concetti

Libreria di Utilità

Stringhe

Contenitori

Algoritmi

Iteratori

Libreria matematca

Input/output

Localizzazione

Espressioni regolari (C++11)

Operazioni atomicche (C++11)

Multithreading (C++11)

 

Contenitori libreria

array (C++11)

vector

deque

forward_list (C++11)

list

set

multiset

map

multimap

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

stack

queue

priority_queue

 

std::vector

Membri funzioni Original: Member functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

vector::vector

vector::~vector

vector::operator=

vector::assign

vector::get_allocator

Elemento accesso Original: Element access The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

vector::at

vector::operator[]

vector::front

vector::back

vector::data (C++11)

Iteratori Original: Iterators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

vector::begin vector::cbegin (C++11)

vector::end vector::cend (C++11)

vector::rbegin vector::crbegin (C++11)

vector::rend vector::crend (C++11)

Capacità Original: Capacity The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

vector::empty

vector::size

vector::max_size

vector::reserve

vector::capacity

vector::shrink_to_fit (C++11)

Modificatori Original: Modifiers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

vector::clear

vector::insert

vector::emplace (C++11)

vector::erase

vector::push_back

vector::emplace_back (C++11)

vector::pop_back

vector::resize

vector::swap

 

<tbody> </tbody>

reference front();
const_reference front() const;

Restituisce un riferimento al primo elemento nel contenitore.

Original:

Returns a reference to the first element in the container.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Chiamare front su un contenitore vuoto non è definito.

Original:

Calling front on an empty container is undefined.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Parametri

(Nessuno)

Original:

(none)

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Valore di ritorno

riferimento al primo elemento

Original:

reference to the first element

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Complessità

Constant

Original:

Constant

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Note

Per un c contenitore, il c.front() espressione è equivalente a *c.begin().

Original:

For a container c, the expression c.front() is equivalent to *c.begin().

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Esempio

Il codice seguente utilizza front per visualizzare il primo elemento di un std::vector<char>:

Original:

The following code uses front to display the first element of a std::vector<char>:

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

#include <vector>
#include <iostream>
 
int main()
{
    std::vector<char> letters {'o', 'm', 'g', 'w', 't', 'f'};
 
    if (!letters.empty()) {
        std::cout << "The first character is: " << letters.front() << '\n';
    }  
}

Output:

The first character is o

See also

back	access the last element (metodo pubblico)