std::forward_list remove() method

since C++20

// (1) Non const version only
size_type remove( const T& value );

// (2) Non const version only
template< class UnaryPredicate >
size_type remove_if( UnaryPredicate p );

since C++11

// (1) Non const version only
void remove( const T& value );

// (2) Non const version only
template< class UnaryPredicate >
void remove_if( UnaryPredicate p );

Removes all elements satisfying specific criteria.

• (1) Removes all elements that are equal to value.
• (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.

Return value

The number of elements removed. (since C++20)
(none) (until C++20)

Complexity

Linear in the size of the container - O(size()).

Exceptions

(none)

Notes

Feature testing macro: __cpp_lib_generic_associative_lookup.

Example

Main.cpp

#include <forward_list>
#include <iostream>
 
int main()
{
    std::forward_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