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std::copy, std::copy_if

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C++
 
Algorithm Bibliothek
Funktionen
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Functions
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Nicht-modifizierende Sequenz Operationen
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Non-modifying sequence operations
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Modifizierende Sequenz Operationen
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Modifying sequence operations
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Partitionierungsoperationen
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Partitioning operations
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Sortierung Operationen (auf sortierten Bereiche)
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Sorting operations (on sorted ranges)
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Binary Suchaktionen (auf sortierten Bereiche)
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Binary search operations (on sorted ranges)
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Set-Operationen (auf sortierten Bereiche)
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Set operations (on sorted ranges)
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Heap-Operationen
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Heap operations
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Minimum / Maximum Operationen
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Minimum/maximum operations
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Numerische Operationen
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Numeric operations
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C-Bibliothek
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C library
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definiert in 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) (seit C++11)
Kopiert die Elemente im Bereich von [first, last) definiert, in einen anderen Bereich beginnend bei d_first. Die zweite Funktion kopiert nur die Elemente, für die das Prädikat pred kehrt 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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Inhaltsverzeichnis

[Bearbeiten] Parameter

first, last -
der Bereich der zu kopierenden Elemente
Original:
the range of elements to copy
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d_first -
der Beginn des Zielbereichs. Wenn d_first in [first, last) ist, muss std::copy_backward statt std::copy verwendet werden .
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
für die erforderlichen Elemente
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.

[Bearbeiten] Rückgabewert

Output Iterator auf das Element in den Zielbereich kopiert, ein nach dem letzten Element .
Original:
Output iterator to the element in the destination range, one past the last element copied.
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[Bearbeiten] Komplexität

1)
Genau last - first Aufgaben
Original:
Exactly last - first assignments
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2)
Genau last - first Anwendungen des Prädikats
Original:
Exactly last - first applications of the predicate
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[Bearbeiten] Notes

In der Praxis vermeiden Implementierungen std::copy mehrere Zuweisungen und Nutzung Bulk-Copy-Funktionen wie std::memcpy wenn der Werttyp ist 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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[Bearbeiten] Mögliche Implementierung

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;
}

[Bearbeiten] Beispiel

Der folgende Code verwendet copy sowohl kopieren Sie den Inhalt eines Vektors zu einem anderen und um das resultierende Vektor:
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

[Bearbeiten] Siehe auch
Kopien einen Bereich von Elementen in rückwärts um
Original:
copies a range of elements in backwards order
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(Funktions-Template) [edit]
Kopiert einen Bereich von Elementen ohne die Seiten, die bestimmte Kriterien erfüllen
Original:
copies a range of elements omitting those that satisfy specific criteria
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(Funktions-Template) [edit]
Von „https://de.cppreference.com/mwiki/index.php?title=cpp/algorithm/copy&oldid=26087“