# std::ranges::range_adaptor_closure

From cppreference.com
< cpp‎ | ranges

Defined in header `<ranges>` |  |
template< class D > requires std::is_object_v<D> && std::same_as<D, std::remove_cv_t<D>> class range_adaptor_closure {}; |  | (since C++23)

`std::ranges::range_adaptor_closure` is a helper class template for defining a RangeAdaptorClosureObject.

Let `t` be the object of type `T`, the implementation ensures that `t` is a range adaptor closure object if all the requirements are met:

- `t` is a unary function object that takes one `range` argument.
- `T` has exactly one public base class ranges::range_adaptor_closure<T>, and T has no base classes of type ranges::range_adaptor_closure<U> for any other type U.
- `T` does not satisfy `range`.

### Example

Run this code

    #include <iostream>
    #include <ranges>
    #include <string>
    #include <string_view>

    // define Slice as a range adaptor closure
    struct Slice : std::ranges::range_adaptor_closure<Slice> {
        std::size_t start = 0;
        std::size_t end = std::string_view::npos;

        std::string_view operator()(std::string_view sv) const {
            return sv.substr(start, end - start);
        }
    };

    int main() {
        std::string str = "01234567";

        Slice slicer{.start = 1, .end = 6};

        auto sv1 = slicer(str);  // use slicer as a normal function object
        auto sv2 = str | slicer; // use slicer as a range adaptor closure object
        std::cout << sv1 << '\n';
        std::cout << sv2 << '\n';

        // range adaptor closures can be composed
        auto slice_and_drop = slicer
                            | std::views::drop_while([](auto ch) { return ch != '3'; });
        std::cout << std::string_view(str | slice_and_drop) << '\n';
    }

Output:

    12345
    12345
    345

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/ranges/range_adaptor_closure&oldid=151128"