std::copy, std::copy_if — cppreference.com

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Déclaré dans l'en-tête `<algorithm>`
`template< class InputIt, class OutputIt > OutputIt copy( InputIt first, InputIt last, OutputIt d_first );`	(1)
`template< class InputIt, class OutputIt, class UnaryPredicate > OutputIt copy_if( InputIt first, InputIt last, OutputIt d_first, UnaryPredicate pred );`	(2)	(depuis C++11)

Copier les éléments de la gamme, défini par [first, last), dans un autre intervalle au début d_first. La deuxième fonction ne copie que les éléments pour lesquels le prédicat renvoie pred true .

Original:

Copies the elements in the range, defined by [first, last), to another range beginning at d_first. The second function only copies the elements for which the predicate pred returns true.

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Paramètres

first, last	-	l'éventail des éléments à copier Original: the range of elements to copy The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
d_first	-	le début de la plage de destination. Si `d_first` est dans `[first, last)`, std::copy_backward doit être utilisé à la place de std::copy . Original: the beginning of the destination range. If `d_first` is within `[first, last)`, std::copy_backward must be used instead of std::copy. The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
pred	-	prédicat unéaire qui retourne `true` pour les éléments requis Original: for the required elements The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. . L'expression `pred(v)` doit pouvoir être convertie à `bool` pour tout argument `v` de type (possiblement const) `VT`, où `VT` est le type de valeur de `InputIt`, inconditionellement de value category, et ne doit pas modifier `v`. Ainsi, un type-paramètre `VT&`n'est pas permis ainsi que pour `VT` sauf pour `VT` un déplacement est équivalent à une copie (depuis C++11).
Type requirements
-`InputIt` must meet the requirements of `InputIterator`.
-`OutputIt` must meet the requirements of `OutputIterator`.

Retourne la valeur

Itérateur de sortie de l'élément dans la zone de destination, une après le dernier élément copié .

Original:

Output iterator to the element in the destination range, one past the last element copied.

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Complexité

Exactement last - first missions

Original:

Exactly last - first assignments

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Exactement last - first applications du prédicat

Original:

Exactly last - first applications of the predicate

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Notes

Dans la pratique, les implémentations de std::copy évitent les affectations multiples et utilisent des fonctions de copie binaire telles que std::memmove si le type de valeur est TriviallyCopyable

Original:

In practice, implementations of std::copy avoid multiple assignments and use bulk copy functions such as std::memcpy if the value type is TriviallyCopyable

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Mise en œuvre possible

First version
template<class InputIt, class OutputIt> OutputIt copy(InputIt first, InputIt last, OutputIt d_first) { while (first != last) { d_first++ = first++; } return d_first; }
Second version
template<class InputIt, class OutputIt, class UnaryPredicate> OutputIt copy_if(InputIt first, InputIt last, OutputIt d_first, UnaryPredicate pred) { while (first != last) { if(pred(first)) d_first++ = *first; first++; } return d_first; }

First version

template<class InputIt, class OutputIt>
OutputIt copy(InputIt first, InputIt last, 
              OutputIt d_first)
{
    while (first != last) {
        *d_first++ = *first++;
    }
    return d_first;
}

Second version

template<class InputIt, class OutputIt, class UnaryPredicate>
OutputIt copy_if(InputIt first, InputIt last, 
                 OutputIt d_first, UnaryPredicate pred)
{
    while (first != last) {
        if(pred(*first))
            *d_first++ = *first;
         first++;
    }
    return d_first;
}

Exemple

Le code suivant utilise la copie à la fois sur le contenu d'un vecteur à l'autre et d'afficher le vecteur résultant:

Original:

The following code uses copy to both copy the contents of one vector to another and to display the resulting vector:

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#include <algorithm>
#include <iostream>
#include <vector>
#include <iterator>
 
int main()
{
    std::vector<int> from_vector;
    for (int i = 0; i < 10; i++) {
        from_vector.push_back(i);
    }
 
    std::vector<int> to_vector(10);
 
    std::copy(from_vector.begin(), from_vector.end(), to_vector.begin());
 
    std::cout << "to_vector contains: ";
    std::copy(to_vector.begin(), to_vector.end(), 
              std::ostream_iterator<int>(std::cout, " "));
    std::cout << std::endl;
}

Résultat :

to_vector contains: 0 1 2 3 4 5 6 7 8 9

Voir aussi


	copie une plage d'éléments dans l'ordre inverse Original: copies a range of elements in backwards order The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (fonction générique) [edit]

	Copie une série d'éléments en omettant ceux qui satisfont à certains critères Original: copies a range of elements omitting those that satisfy specific criteria The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (fonction générique) [edit]