remove


Category: algorithms	Component type: function

Prototype

template <class ForwardIterator, class T>
ForwardIterator remove(ForwardIterator first, ForwardIterator last,
                       const T& value);

Description

Remove removes from the range [first, last) all elements that are equal to value. That is, remove returns an iterator new_last such that the range [first, new_last) contains no elements equal to value. [1] The iterators in the range [new_last, last) are all still dereferenceable, but the elements that they point to are unspecified. Remove is stable, meaning that the relative order of elements that are not equal to value is unchanged.

Definition

Defined in the standard header algorithm, and in the nonstandard backward-compatibility header algo.h.

Requirements on types

ForwardIterator is a model of Forward Iterator.
ForwardIterator is mutable.
T is a model of Equality Comparable.
Objects of type T can be compared for equality with objects of ForwardIterator's value type.

Preconditions

[first, last) is a valid range.

Complexity

Linear. Remove performs exactly last - first comparisons for equality.

Example

vector<int> V;
V.push_back(3);
V.push_back(1);
V.push_back(4);
V.push_back(1);
V.push_back(5);
V.push_back(9);

copy(V.begin(), V.end(), ostream_iterator<int>(cout, " "));
    // The output is "3 1 4 1 5 9".

vector<int>::iterator new_end = remove(V.begin(), V.end(), 1);
copy(V.begin(), new_end, ostream_iterator<int>(cout, " "));
    // The output is "3 4 5 9".

Notes

[1] The meaning of "removal" is somewhat subtle. Remove 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(V.begin(), V.end(), 0) does not change V.size(): V will contain just as many elements as it did before. Remove 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(S.begin(), S.end(), x), S.end()).