NAME¶

std::list::erase - std::list::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).

References and iterators to the erased elements are invalidated. Other references
and iterators are not affected.

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

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¶

(none)

Complexity¶

1) Constant.
2) Linear in the distance between first and last.

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

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

int main()
{
std::list<int> c{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
print_container(c);

c.erase(c.begin());
print_container(c);

std::list<int>::iterator range_begin = c.begin();
std::list<int>::iterator range_end = c.begin();
std::advance(range_begin, 2);
std::advance(range_end, 5);

c.erase(range_begin, range_end);
print_container(c);

// Erase all even numbers
for (std::list<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 dereferenceable, which not required if
LWG 151 C++98 made the behavior of clearing an empty list first == last
undefined

See also¶

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