Introduction to make_move_iterator in C++

The make_move_iterator function in C++ provides a convenient way to create move iterators from ordinary iterators.

When iterating through a range of objects with an ordinary iterator, each object in the range is copied into the temporary variables used by the iterator's dereference and increment operators. However, this can be inefficient when iterating over large objects or containers.

Move iterators, on the other hand, perform move semantics instead of copy semantics. This means that each object in the range is moved into the temporary variables, which is more efficient and can be important for performance-critical code.

Syntax

The make_move_iterator function is defined in the <iterator> header file and has the following syntax:

template <class Iterator>
move_iterator<Iterator> make_move_iterator(Iterator i);

This function takes an ordinary iterator i of any pointer or iterator type and returns a move iterator of the same type.

Example

Suppose we have a vector of large objects that we want to iterate over while performing a move operation on each element:

std::vector<LargeObject> vec;

// fill the vector with large objects...

for (auto&& obj : vec) {
    // perform a move operation on each object...
}

Using an ordinary iterator, each object in the vector would be copied into the temporary variable used by the dereference operator, which could be slow for large objects.

By using a move iterator instead, we can perform the same operation more efficiently:

for (auto&& obj : std::make_move_iterator(vec.begin()), std::make_move_iterator(vec.end())) {
    // perform a move operation on each object...
}

Here, we create a move iterator from the beginning and end of the vector using the make_move_iterator function, and then use it to iterate over the vector while performing a move operation on each object.

Conclusion

In conclusion, the make_move_iterator function provides a powerful tool for optimizing performance when iterating over large objects or containers. By using move semantics instead of copy semantics, move iterators can be much more efficient and can make a significant difference for performance-critical code.