std::ranges::range_adaptor_closure - cppreference.com (original) (raw)

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.

[edit] Notes

[edit] Example

#include #include   // Define Slice as a range adaptor closure struct Slice : std::ranges::range_adaptor_closure { 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};   // use slicer as a normal function object constexpr auto sv1 = slicer(str); static_assert(sv1 == "12345");   // use slicer as a range adaptor closure object constexpr auto sv2 = str | slicer; static_assert(sv2 == "12345");   // range adaptor closures can be composed constexpr auto slice_and_drop = slicer | std::views::drop(2); static_assert(std::string_view(str | slice_and_drop) == "345"); }