|Category: algorithms||Component type: function|
template <class ForwardIterator, class Predicate> ForwardIterator remove_if(ForwardIterator first, ForwardIterator last, Predicate pred);
vector<int> V; V.push_back(1); V.push_back(4); V.push_back(2); V.push_back(8); V.push_back(5); V.push_back(7); copy(V.begin(), V.end(), ostream_iterator<int>(cout, " ")); // The output is "1 4 2 8 5 7" vector<int>::iterator new_end = remove_if(V.begin(), V.end(), compose1(bind2nd(equal_to<int>(), 0), bind2nd(modulus<int>(), 2))); V.erase(new_end, V.end());  copy(V.begin(), V.end(), ostream_iterator<int>(cout, " ")); // The output is "1 5 7".
 The meaning of "removal" is somewhat subtle. Remove_if does not destroy any iterators, and does not change the distance between first and last. (There's no way that it could do anything of the sort.) So, for example, if V is a vector, remove_if(V.begin(), V.end(), pred) does not change V.size(): V will contain just as many elements as it did before. Remove_if returns an iterator that points to the end of the resulting range after elements have been removed from it; it follows that the elements after that iterator are of no interest, and may be discarded. If you are removing elements from a Sequence, you may simply erase them. That is, a reasonable way of removing elements from a Sequence is S.erase(remove_if(S.begin(), S.end(), pred), S.end()).