Creating your own range view

The C++20 ranges library simplifies the handling of ranges of elements. The 16 range adaptors (views) defined in the library provide useful operations, as seen in the previous recipe. However, you can create your own view that can be used together with the standard ones. In this recipe, you will learn how to do that. We will create a view called trim that, given a range and a unary predicate, returns a new range without the front and back elements that satisfy the predicate.

Getting ready

In this recipe, we will use the same namespace aliases used in the previous one, with rg as an alias for std::ranges and rv as an alias for std::ranges::views.

How to do it...

To create a view, do the following:

• Create a class template, called trim_view, derived from std::ranges::view_interface:

  template<rg::input_range R, typename P>
      requires rg::view<R>
  class trim_view :
      public rg::view_interface<trim_view<...