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Varianti

std::copy, std::copy_if

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C++
 
Algoritmo libreria
Funzioni
Original:
Functions
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Non modifica le operazioni di sequenza
Original:
Non-modifying sequence operations
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Modifica delle operazioni di sequenza
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Modifying sequence operations
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Partizionamento operazioni
Original:
Partitioning operations
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Ordinamento delle operazioni (su intervalli ordinati)
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Sorting operations (on sorted ranges)
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Binarie (le operazioni di ricerca sui campi ordinati)
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Binary search operations (on sorted ranges)
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Impostare le operazioni (su intervalli ordinati)
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Set operations (on sorted ranges)
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Heap operazioni
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Heap operations
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Minimo / massimo le operazioni
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Minimum/maximum operations
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Operazioni numeriche
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Numeric operations
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Libreria C
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C library
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Elemento definito nell'header <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) (dal C++11)
Copia gli elementi della gamma, definiti da [first, last), a un altro inizio gamma a d_first. La seconda funzione copia solo gli elementi per i quali il predicato pred ritorna 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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Indice

[modifica] Parametri

first, last -
dell'intervallo di elementi da copiare
Original:
the range of elements to copy
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d_first -
l'inizio del campo di destinazione. Se d_first è all'interno [first, last), std::copy_backward deve essere usato al posto di 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.
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pred - unary predicate which returns ​true
per gli elementi richiesti
Original:
for the required elements
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.

The signature of the predicate function should be equivalent to the following:

 bool pred(const Type &a);

The signature does not need to have const &, but the function must not modify the objects passed to it.
The type Type must be such that an object of type InputIt can be dereferenced and then implicitly converted to Type. ​

Type requirements
-
InputIt must meet the requirements of InputIterator.
-
OutputIt must meet the requirements of OutputIterator.

[modifica] Valore di ritorno

Iteratore di uscita per l'elemento nel campo di destinazione, un passato l'ultimo elemento copiato.
Original:
Output iterator to the element in the destination range, one past the last element copied.
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[modifica] Complessità

1)
Esattamente last - first assegnazioni
Original:
Exactly last - first assignments
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2)
Esattamente last - first applicazioni del predicato
Original:
Exactly last - first applications of the predicate
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[modifica] Note

In pratica, le implementazioni di std::copy evitare assegnazioni multiple e l'uso di copia di massa funzioni come std::memcpy se il tipo di valore è 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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[modifica] Possibile implementazione

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;
}

[modifica] Esempio

Il codice seguente utilizza copia sia a copiare il contenuto di un vettore ad un altro e per visualizzare il vettore risultante:
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;
}

Output: 

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

[modifica] Vedi anche
una serie di elementi in ordine inverso
Original:
copies a range of elements in backwards order
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(funzione di modello) [modifica]
copia un intervallo di elementi omettendo quelli che soddisfano criteri specifici
Original:
copies a range of elements omitting those that satisfy specific criteria
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(funzione di modello) [modifica]
Estratto da "https://it.cppreference.com/mwiki/index.php?title=cpp/algorithm/copy&oldid=24927"