list::remove_if


public member function template
template <class Predicate>
  void remove_if ( Predicate pred );

Remove elements fulfilling condition

Removes from the list all the elements for which Predicate pred returns true. This calls the destructor of these objects and reduces the list size by the amount of elements removed.

Predicate pred can be implemented as any typed expression taking one argument of the same type as the list and returning a bool (this may either be a function pointer or an object whose class implements operator().

The function calls pred(*i) for each element (where i is an iterator to that element). Any of the elements in the list for which this returns true, is removed from the container.

Notice that a global algorithm function, remove_if, exists with a similar behavior but operating between two iterators.

Parameters

pred
Unary predicate that, taking a value of the same type as those contained in the list object, returns true for those values to be removed from the container, and false for those remaining.


Return value

none

Example

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// list::remove_if
#include <iostream>
#include <list>
using namespace std;

// a predicate implemented as a function:
bool single_digit (const int& value) { return (value<10); }

// a predicate implemented as a class:
class is_odd
{
public:
  bool operator() (const int& value) {return (value%2)==1; }
};

int main ()
{
  int myints[]= {15,36,7,17,20,39,4,1};
  list<int> mylist (myints,myints+8);   // 15 36 7 17 20 39 4 1

  mylist.remove_if (single_digit);      // 15 36 17 20 39

  mylist.remove_if (is_odd());          // 36 20

  cout << "mylist contains:";
  for (list<int>::iterator it=mylist.begin(); it!=mylist.end(); ++it)
    cout << " " << *it;
  cout << endl;

  return 0;
}


Output:
mylist contains: 36 20


Complexity

Linear in list::size (predicates).

See also

list::remove Remove elements with specific value (public member function)
list::erase Erase elements (public member function)
list::unique Remove duplicate values (member function)
list::pop_back Delete last element (public member function)
list::pop_front Delete first element (public member function)