Mutable changes with actions

In addition to views, the ranges library offers actions. Actions allow eager, mutable operations. For example, to sort the values in the same vector, we can use the following syntax:

TEST_CASE("Sort numbers"){
    vector<int> numbers{1, 12, 5, 20, 2, 10, 17, 25, 4};
    vector<int> expected{1, 2, 4, 5, 10, 12, 17, 20, 25};

    numbers |= ranges::action::sort;

    CHECK_EQ(expected, numbers);
}

The |= operator is similar to the ranges::action::sort(numbers) call, sorting the vector in place. Actions are also composable, either through a direct method call or with the | operator. This allows allows us to write code that sorts and keeps the unique items from a container through composition of the sort and unique actions with the | operator:

TEST_CASE("Sort numbers and pick unique"){
    vector<int> numbers{1, 1, 12, 5,...