#include <ranges>#include <span>#include <string_view>#include <vector> // mechanisms for ensuring the parameter is a constant range// 1) an overload set where the mutable one defers to the constant onetemplate<std::ranges::constant_range R>void takes_any_range1(R&& r){// R is definitely a constant range} template<std::ranges::range R>void takes_any_range1(R&& r){    takes_any_range1(std::views::as_const(std::forward<R>(r)));} // 2) one function template that shadows its parametertemplate<std::ranges::range R>void takes_any_range2(R&& _r){auto r= std::views::as_const(std::forward<R>(_r)); // r is definitely a constant range// never use _r again} // 3) one function template that recursively invokes itselftemplate<std::ranges::range R>void takes_any_range3(R&& r){ifconstexpr(std::ranges::constant_range<R>){// R is definitely a constant range// put implementation here}else        takes_any_range3(std::views::as_const(std::forward<R>(r)));} static_assert(        std::ranges::constant_range<conststd::vector<int>> and    not std::ranges::constant_range<std::vector<int>> and        std::ranges::constant_range<std::string_view> and    not std::ranges::constant_range<std::span<int>> and        std::ranges::constant_range<std::span<constint>> and    not std::ranges::constant_range<conststd::span<int>>); int main(){}