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Language: C++
Expertise: Intermediate

Dec 6, 2004

Insert iterators come in very handy when you need to populate a container using an STL algorithm which uses an assignment operator to fill in the data:

int iArr [] = {2, 2, 3, 4, 5, 6, 7};

#include <vector>
vector<int> vecInt;

For example, the following statement will fail because vecInt is not allocated space and the unique_copy() algorithm uses this assignment operator:

#include <algorithm>
unique_copy (iArr, iArr+7, vecInt.begin());

Conversely, using back_inserter() as the third argument causes the container to invoke push_back() instead of the assignment operator.

#include <iterator>
unique_copy (iArr, iArr+7, back_inserter(vecInt));

The other kind of insert iterator is front_inserter(). Be sure before using these that the underlying container supports the functions they invoke in place of the assignment operator. For instance, push_front() in place of the assignment operator, and vector does not support push_front().