C++ High Performance

Views

Views might seem similar to actions, but on the inside, they are completely different. While an action operates on the input container and returns a mutated version, views simply return a proxy view, which, when iterated, looks like a mutated container.

However, the container is not mutated at all; all the processing is performed in the iterators.

Comparing ranges::view::transform() with ranges::action::transform()clarifies the difference. As actions transforms the container, they cannot transform the type, whereas views can transform to a view of any type.

The following transformation, where an int is transformed to a std::string, can only be performed using ranges::view. Note that str_view is just a proxy; the actual returned string ...