C++ Forward_list Library - remove_if() Function

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Description

The C++ function std::forward_list::remove_if() removes elements from the forward_list that fulfills the condition. It removes all elements for which predicate returns true.

Declaration

Following is the declaration for std::forward_list::remove_if() function form std::forward_list header.

C++11

template <class Predicate>
void remove_if (Predicate pred);

Parameters

pred − Unary predicate that, which takes a value of the same type and returns true for those values to be removed from the container.

Return value

None

Exceptions

If pred is guaranteed to no_throw, then function never throws exceptions.

Time complexity

Linear i.e. O(n)

Example

The following example shows the usage of std::forward_list::remove_if() function.

#include <iostream>
#include <forward_list>

using namespace std;

bool foo(int n) {
   return (n > 5);
}

int main(void) {

   forward_list<int> fl = {1, 2, 3, 4, 5, 6, 7, 8, 9};

   cout << "List contents before remove operation" << endl;

   for (auto it = fl.begin(); it != fl.end(); ++it)
      cout << *it << endl;

   /* remove all elements greater than 5 */
   fl.remove_if(foo);

   cout << "List contents after remove operation" << endl;

   for (auto it = fl.begin(); it != fl.end(); ++it)
      cout << *it << endl;

   return 0;
}

Let us compile and run the above program, this will produce the following result −

List contents before remove operation
1
2
3
4
5
6
7
8
9
List contents after remove operation
1
2
3
4
5