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std::iterator_traits – cppreference.com

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definiert in Header

<iterator>

template< class Iterator> struct iterator_traits;

template< class T > struct iterator_traits<T*>;

template< class T > struct iterator_traits<const T*>;

std::iterator_traits ist die Art Trait-Klasse, die einheitliche Schnittstelle zu den Eigenschaften des Iterator-Typen. Dies macht es möglich, Algorithmen nur hinsichtlich Iteratoren implementieren .

Original:

std::iterator_traits is the type trait class that provides uniform interface to the properties of iterator types. This makes it possible to implement algorithms only in terms of iterators.

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Mitglied Typen

Mitglied Typ

Original:

Member type

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 Definition
difference_type Iterator::difference_type
value_type Iterator::value_type
pointer Iterator::pointer
reference Iterator::reference
iterator_category Iterator::iterator_category

Spezialisierungen

Diese Art Charakterzug kann spezialisiert für Typen, die als Iteratoren verwendet werden kann vom Benutzer zur Verfügung gestellt werden. Die Standard-Bibliothek bietet zwei partielle Spezialisierungen für Zeigertypen T *, die es ermöglicht, alle Iterator-basierte Algorithmen mit rohen Zeigern macht .

Original:

This type trait may be specialized for user-provided types that may be used as iterators. The standard library provides two partial specializations for pointer types T*, which makes it possible to use all iterator-based algorithms with raw pointers.

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T * Spezialisierung Mitglied Typen

Mitglied Typ

Original:

Member type

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 Definition
difference_type std::ptrdiff_t
value_type T
pointer T*
reference T&
iterator_category std::random_access_iterator_tag

const T * Spezialisierung Mitglied Typen

Mitglied Typ

Original:

Member type

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 Definition
difference_type std::ptrdiff_t
value_type T
pointer const T*
reference const T&
iterator_category std::random_access_iterator_tag

Beispiel

Allzweck-reverse ()-Implementierung für bidirektionale Iteratoren

Original:

general-purpose reverse() implementation for bidirectional iterators

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#include <iostream>
#include <iterator>
#include <vector>
#include <list>

template<class BDIter>
void my_reverse(BDIter first, BDIter last)
{
    typename std::iterator_traits<BDIter>::difference_type n = std::distance(first, last);
    --n;
    while(n > 0) {
        typename std::iterator_traits<BDIter>::value_type tmp = *first;
        *first++ = *--last;
        *last = tmp;
        n -= 2;
    }
}

int main()
{
    std::vector<int> v{1,2,3,4,5};
    my_reverse(v.begin(), v.end());
    for(int n : v)
        std::cout << n << ' ';
    std::cout << '\n';

    std::list<int> l{1,2,3,4,5};
    my_reverse(l.begin(), l.end());
    for(auto n : l)
        std::cout << n << ' ';
    std::cout << '\n';

//    std::istreambuf_iterator<char> i1(std::cin), i2;
//    my_reverse(i1, i2); // compilation error

}

Output:

Siehe auch