What are the differences between std::transform and std::transform_iterator in C++11?

What are the differences between std::transform and std::transform_iterator in C++11?

std::transform is an algorithm that applies a function to a range of elements, while std::transform_iterator is an iterator that applies a transformation on-the-fly as you iterate through a range.

Can you give me an example of how to use both?

Sure! For std::transform, you might use it like this:

std::vector<int> vec = {1, 2, 3, 4};
std::vector<int> result;
std::transform(vec.begin(), vec.end(), std::back_inserter(result), [](int x) { return x * 2; });

For std::transform_iterator, it looks like this:

std::vector<int> vec = {1, 2, 3, 4};
auto transform_it = std::make_transform_iterator(vec.begin(), [](int x) { return x * 2; });
for (auto it = transform_it; it != std::make_transform_iterator(vec.end(), [](int x) { return x * 2; }); ++it) {
    std::cout << *it << " ";
}

What are the performance implications of using one over the other?

Using std::transform is generally more straightforward and can be optimized by the compiler. std::transform_iterator, while more flexible, may introduce some overhead due to the function call for each element accessed.

When should I prefer one over the other?

Prefer std::transform when you need a simple transformation of a range. Use std::transform_iterator when you want to apply a transformation lazily or when working with complex data structures.