W3cubDocs

/C++

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

	(1)
void remove( const T& value );		(since C++11) (until C++20)
size_type remove( const T& value );		(since C++20)
	(2)
template< class UnaryPredicate > void remove_if( UnaryPredicate p );		(since C++11) (until C++20)
template< class UnaryPredicate > size_type remove_if( UnaryPredicate p );		(since C++20)

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 (since C++11).

Return value

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

Complexity

Linear in the size of the container.

Notes

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

Example

#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: