NAME¶

std::ranges::range_adaptor_closure - std::ranges::range_adaptor_closure

Synopsis¶

Defined in header <ranges>
template< class D >

requires std::is_object_v<D> && std::same_as<D, (since C++23)
std::remove_cv_t<D>>

class range_adaptor_closure {};

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 <ranges>
#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;

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

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

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

constexpr auto sv1 = slicer(str); // use slicer as a normal function object
constexpr auto sv2 = str | slicer; // use slicer as a range adaptor closure object
static_assert(sv1 == "12345");
static_assert(sv2 == "12345");

// range adaptor closures can be composed
constexpr auto slice_and_drop
= slicer
| std::views::drop_while([](char ch) { return ch != '3'; });
static_assert(std::string_view(str | slice_and_drop) == "345");
}