NAME¶

std::deque::erase - std::deque::erase

Synopsis¶

iterator erase( iterator pos ); (until C++11)
iterator erase( const_iterator pos ); (since C++11)
iterator erase( iterator first, iterator last ); (1) (until C++11)
iterator erase( const_iterator first, (2) (since C++11)
const_iterator last );

Erases the specified elements from the container.

1) Removes the element at pos.
2) Removes the elements in the range [first, last).

All iterators and references are invalidated, unless the erased elements are at the
end or at the beginning of the container, in which case only the iterators and
references to the erased elements are invalidated. The end() iterator is also
invalidated unless the erased elements are at the beginning of the container and the
last element is not erased.

The iterator pos must be valid and dereferenceable. Thus the end() iterator (which
is valid, but is not dereferenceable) cannot be used as a value for pos.

The iterator first does not need to be dereferenceable if first == last: erasing an
empty range is a no-op.

Parameters¶

pos - iterator to the element to remove
first, last - range of elements to remove

Type requirements¶

-
T must meet the requirements of MoveAssignable.

Return value¶

Iterator following the last removed element.

1) If pos refers to the last element, then the end() iterator is returned.
2) If last == end() prior to removal, then the updated end() iterator is returned.
If [first, last) is an empty range, then last is returned.

Exceptions¶

Does not throw unless an exception is thrown by the assignment operator of T.

Complexity¶

Linear: the number of calls to the destructor of T is the same as the number of
elements erased, the number of calls to the assignment operator of T is no more than
the lesser of the number of elements before the erased elements and the number of
elements after the erased elements.

Notes¶

When container elements need to be erased based on a predicate, rather than
iterating the container and calling unary erase, the iterator range overload is
generally used with std::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)

Example¶

// Run this code

#include <deque>
#include <iostream>

void print_container(const std::deque<int>& c)
{
for (int i : c)
std::cout << i << ' ';
std::cout << '\n';
}

int main()
{
std::deque<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 numbers
for (std::deque<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 9
1 2 3 4 5 6 7 8 9
1 2 6 7 8 9
1 7 9

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
first was required to be
LWG 151 C++98 dereferenceable, which not required if
made the behavior of clearing an empty first == last
deque undefined
it is invalidated if the
LWG 638 C++98 the past-the-end iterator was not elements are
invalidated erased from the middle or
the end

See also¶

erase(std::deque) erases all elements satisfying specific criteria
erase_if(std::deque) (function template)
(C++20)
clear clears the contents
(public member function)