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

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    [edit template]
     
    C++
     
    Containers library
     
    std::list
    Member functions
    Non-member functions
    (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
    Deduction guides(C++17)
     
    (1)
    void remove( const T& value );
    		 (until C++20)
    size_type remove( const T& value );
    		 (since C++20)
    (2)
    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.

    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.

    Return value

    (none)

    		(until C++20)

    The number of elements removed.

    		(since C++20)

    Complexity

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

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

    Notes

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

    Example

    Run this code
    #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';
}

    Output: 

    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

    See also

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