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

 

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std::forward_list

Member functions
forward_list::forward_list forward_list::~forward_list forward_list::operator= forward_list::assign forward_list::assign_range (C++23)   forward_list::get_allocator Element access forward_list::front Iterators forward_list::before_beginforward_list::cbefore_begin forward_list::beginforward_list::cbegin forward_list::endforward_list::cend Capacity forward_list::empty forward_list::max_size	Modifiers forward_list::clear forward_list::emplace_front forward_list::push_front forward_list::insert_after forward_list::emplace_after forward_list::erase_after forward_list::insert_range_after (C++23) forward_list::prepend_range (C++23) forward_list::pop_front forward_list::resize forward_list::swap Operations forward_list::merge forward_list::splice_after forward_list::removeforward_list::remove_if forward_list::reverse forward_list::unique forward_list::sort
Non-member functions
operator==operator<=> (C++20) swap(std::forward_list) erase(std::forward_list)erase_if(std::forward_list) (C++20)(C++20)	operator!=operator<operator>operator<=operator>= (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 );			(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. 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 \(\scriptsize N\)N as std::distance(begin(), end()):

1) Exactly \(\scriptsize N\)N comparisons using operator==.

2) Exactly \(\scriptsize N\)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 <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

See also

removeremove_if

removes elements satisfying specific criteria (function template)