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    std::deque::emplace_back

    De cppreference.com

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    <metanoindex/>

     
    C++
     
    Bibliothèque de conteneurs
     
    std :: deque
    Les fonctions membres
    Original:
    Member functions
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    deque::deque
    deque::~deque
    deque::operator=
    deque::assign
    deque::get_allocator
    Elément d'accès
    Original:
    Element access
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    deque::front
    deque::back
    Les itérateurs
    Original:
    Iterators
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    deque::begin
    deque::cbegin
    (C++11)
    deque::end
    deque::cend
    (C++11)
    deque::rbegin
    deque::crbegin
    (C++11)
    deque::rend
    deque::crend
    (C++11)
    Capacité
    Original:
    Capacity
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    deque::empty
    deque::size
    deque::max_size
    deque::shrink_to_fit
    Modificateurs
    Original:
    Modifiers
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    deque::clear
    deque::insert
    deque::emplace
    deque::erase
    deque::push_front
    deque::emplace_front
    deque::pop_front
    deque::push_back
    deque::emplace_back
    deque::pop_back
    deque::resize
    deque::swap
     
    <tbody> </tbody>
    template< class... Args > void emplace_back( Args&&... args );
    		 (depuis C++11)
    Ajoute un nouvel élément à la fin du récipient. L'élément est réalisé in-situ, c'est à dire pas de copie ou les opérations de déplacement sont effectuées. Le constructeur de l'élément est appelée avec exactement les mêmes arguments qui sont fournis à la fonction .
    Original:
    Appends a new element to the end of the container. The element is constructed in-place, i.e. no copy or move operations are performed. The constructor of the element is called with exactly the same arguments that are supplied to the function.
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    All iterators are invalidated. No references are invalidated.

    Paramètres

    args -
    arguments à transmettre au constructeur de l'élément
    Original:
    arguments to forward to the constructor of the element
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    Retourne la valeur

    (Aucun)
    Original:
    (none)
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    Complexité

    Constant .
    Original:
    Constant.
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    Exemple

    Le code suivant utilise emplace_back d'ajouter un objet de President type à un std::deque. Il démontre comment emplace_back transmet les paramètres au constructeur President et montre comment l'utilisation emplace_back évite la copie supplémentaire ou un déplacement nécessaire lorsque vous utilisez push_back .
    Original:
    The following code uses emplace_back to append an object of type President to a std::deque. It demonstrates how emplace_back forwards parameters to the President constructor and shows how using emplace_back avoids the extra copy or move operation required when using push_back.
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    #include <deque>
#include <string>
#include <iostream>
 
struct President
{
    std::string name;
    std::string country;
    int year;
  
    President(std::string && p_name, std::string && p_country, int p_year)
        : name(std::move(p_name)), country(std::move(p_country)), year(p_year)
    {
        std::cout << "I am being constructed.\n";
    }
    President(President&& other)
        : name(std::move(other.name)), country(std::move(other.country)), year(other.year)
    {
        std::cout << "I am being moved.\n";
    }
    President& operator=(const President& other) = default;
};

int main()
{
    std::deque<President> elections;
    std::cout << "emplace_back:\n";
    elections.emplace_back("Nelson Mandela", "South Africa", 1994);

    std::deque<President> reElections;
    std::cout << "\npush_back:\n";
    reElections.push_back(President("Franklin Delano Roosevelt", "the USA", 1936));
 
    std::cout << "\nContents:\n";
    for (President const& president: elections) {
        std::cout << president.name << " was elected president of "
                  << president.country << " in " << president.year << ".\n";
    }
    for (President const& president: reElections) {
        std::cout << president.name << " was re-elected president of "
                  << president.country << " in " << president.year << ".\n";
    }
}

    Résultat : 

    emplace_back:
I am being constructed.

push_back:
I am being constructed.
I am being moved.

Contents:
Nelson Mandela was elected president of South Africa in 1994.
Franklin Delano Roosevelt was re-elected president of the USA in 1936.

    Voir aussi
    ajoute des éléments à la fin
    Original:
    adds elements to the end
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    (fonction membre publique) [edit]