std::list<T,Allocator>::remove, remove_if

< cpp‎ | container‎ | list
void remove( const T& value );
(until C++20)
size_type remove( const T& value );
(since C++20)
template< class UnaryPredicate >
void remove_if( UnaryPredicate p );
(until C++20)
template< class UnaryPredicate >
size_type remove_if( UnaryPredicate p );
(since C++20)

Removes all elements satisfying specific criteria. Invalidates only the iterators and references to the removed elements.

1) Removes all elements that are equal to value (using operator==).
2) Removes all elements for which predicate p returns true.


[edit] Parameters

value - value of the elements to remove
p - unary predicate which returns ​true if the element should be removed.

The expression p(v) must be convertible to bool for every argument v of type (possibly const) T, regardless of value category, and must not modify v. Thus, a parameter type of T&is not allowed, nor is T unless for T a move is equivalent to a copy(since C++11). ​

Type requirements
UnaryPredicate must meet the requirements of Predicate.

[edit] Return value


(until C++20)

The number of elements removed.

(since C++20)

[edit] Complexity

Given N as std::distance(begin(), end()):

1) Exactly N comparisons using operator==.
2) Exactly N applications of the predicate p.

[edit] Notes

Feature-test macro Value Std Feature
__cpp_lib_list_remove_return_type 201806L (C++20) Change the return type

[edit] Example

#include <list>
#include <iostream>
int main()
    std::list<int> l = {1, 100, 2, 3, 10, 1, 11, -1, 12};
    auto count1 = l.remove(1);
    std::cout << count1 << " elements equal to 1 were removed\n";
    auto count2 = l.remove_if([](int n){ return n > 10; });
    std::cout << count2 << " elements greater than 10 were removed\n";
    std::cout << "Finally, the list contains: ";
    for (int n : l)
        std::cout << n << ' ';
    std::cout << '\n';


2 elements equal to 1 were removed
3 elements greater than 10 were removed
Finally, the list contains: 2 3 10 -1

Defect reports

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

DR Applied to Behavior as published Correct behavior
LWG 1207 C++98 it was unclear whether iterators
and/or references will be invalidated
only invalidates iterators and
references to the removed elements

[edit] See also

removes elements satisfying specific criteria
(function template) [edit]