std::input_iterator_tag, std::output_iterator_tag, std::forward_iterator_tag, std::bidirectional_iterator_tag, std::random_access_iterator_tag
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| Defined in header <iterator>
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| struct input_iterator_tag { }; |
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| struct output_iterator_tag { }; |
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| struct forward_iterator_tag : public input_iterator_tag { }; |
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| struct bidirectional_iterator_tag : public forward_iterator_tag { }; |
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| struct random_access_iterator_tag : public bidirectional_iterator_tag { }; |
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Die leeren Typen
std::input_iterator_tag, std::output_iterator_tag, forward_iterator_tag, bidirectional_iterator_tag und random_access_iterator_tag werden verwendet, um geeignete Algorithmen auf die Kategorie eines Iterators auszuwählen. Für jeden Iterator-Typ, ist ein typedef std::iterator_traits<Iterator>::iterator_category zur Verfügung, welches ist ein Alias für eine dieser fünf tag Typen .Original:
The empty types
std::input_iterator_tag, std::output_iterator_tag, forward_iterator_tag, bidirectional_iterator_tag, and random_access_iterator_tag are used to select appropriate algorithms based on the category of an iterator. For every iterator type, a typedef std::iterator_traits<Iterator>::iterator_category is available, which is an alias to one of these five tag types.The text has been machine-translated via Google Translate.
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[Bearbeiten] Beispiel
Verbreitete Technik zur Auswahl eines Algorithmus auf Iteratorkategorie Tags zugrunde, einen Dispatcher-Funktion verwenden (die Alternative ist std :: enable_if)
Original:
Common technique for algorithm selection based on iterator category tags is to use a dispatcher function (the alternative is std::enable_if)
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#include <iostream> #include <vector> #include <list> #include <iterator> template< class BDIter > void alg(BDIter, BDIter, std::bidirectional_iterator_tag) { std::cout << "alg() called for bidirectional iterator\n"; } template <class RAIter> void alg(RAIter, RAIter, std::random_access_iterator_tag) { std::cout << "alg() called for random-access iterator\n"; } template< class Iter > void alg(Iter first, Iter last) { alg(first, last, typename std::iterator_traits<Iter>::iterator_category()); } int main() { std::vector<int> v; alg(v.begin(), v.end()); std::list<int> l; alg(l.begin(), l.end()); // std::istreambuf_iterator<char> i1(std::cin), i2; // alg(i1, i2); // compile error: no matching function for call }
Output:
alg() called for random-access iterator alg() called for bidirectional iterator
[Bearbeiten] Siehe auch
| die grundlegende Iterator Original: the basic iterator The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Klassen-Template) | |
| bietet einheitliche Schnittstelle zu den Eigenschaften eines Iterators Original: provides uniform interface to the properties of an iterator The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (Klassen-Template) | |
