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| Iterator invalidation | ||||
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| Deduction guides(C++17) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| (1) | ||
iterator erase( iterator pos); | (until C++11) | |
iterator erase( const_iterator pos); | (since C++11) (constexpr since C++20) | |
| (2) | ||
iterator erase( iterator first, iterator last); | (until C++11) | |
iterator erase( const_iterator first, const_iterator last); | (since C++11) (constexpr since C++20) | |
Erases the specified elements from the container.
[first, last).Iterators (including theend() iterator) and references to the elements at or after the point of the erase are invalidated.
The iteratorpos must be valid and dereferenceable. Thus theend() iterator (which is valid, but is not dereferenceable) cannot be used as a value forpos.
The iteratorfirst does not need to be dereferenceable iffirst== last: erasing an empty range is a no-op.
Contents |
| pos | - | iterator to the element to remove |
| first, last | - | the pair of iterators defining therange of elements to remove |
| Type requirements | ||
-IfT is notMoveAssignable, the behavior is undefined. | ||
Iterator following the last removed element.
[first, last) is an empty range, thenlast is returned.Does not throw unless an exception is thrown by the assignment operator ofT.
Linear: the number of calls to the destructor ofT is the same as the number of elements erased, the assignment operator ofT is called the number of times equal to the number of elements in the vector after the erased elements.
When container elements need to be erased based on a predicate, rather than iterating the container and calling unaryerase, the iterator range overload is generally used withstd::remove()/std::remove_if() to minimise the number of moves of the remaining (non-removed) elements, — this is the erase-remove idiom.std::erase_if() replaces the erase-remove idiom.(since C++20)
#include <vector>#include <iostream> void print_container(conststd::vector<int>& c){for(int i: c)std::cout<< i<<' ';std::cout<<'\n';} int main(){std::vector<int> c{0,1,2,3,4,5,6,7,8,9}; print_container(c); c.erase(c.begin()); print_container(c); c.erase(c.begin()+2, c.begin()+5); print_container(c); // Erase all even numbersfor(std::vector<int>::iterator it= c.begin(); it!= c.end();){if(*it%2==0) it= c.erase(it);else++it;} print_container(c);}
Output:
0 1 2 3 4 5 6 7 8 91 2 3 4 5 6 7 8 91 2 6 7 8 91 7 9
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 151 | C++98 | first was required to be dereferenceable, which made the behavior of clearing an empty vector undefined | not required if first== last |
| LWG 414 | C++98 | iterators at the point of erase were not invalidated | they are also invalidated |
| erases all elements satisfying specific criteria (function template)[edit] | |
| clears the contents (public member function)[edit] |
