std::forward_list::remove,remove_if(3)

NAME
std::forward_list::remove,remove_if - std::forward_list::remove,remove_if

Synopsis
   void remove( const T& value ); (since C++11)
                        (until C++20)
   size_type remove( const T& value ); (since C++20)
   template< class UnaryPredicate > (1) (since C++11)
   void remove_if( UnaryPredicate p ); (2) (until C++20)
   template< class UnaryPredicate > (since C++20)
   size_type remove_if( UnaryPredicate p );
   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
           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
   p - (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
   remove removes elements satisfying specific criteria
   remove_if (function template)