26 Ranges library [ranges]

The range conversion functions construct an object (usually a container) from a range, by using a constructor taking a range, a from_range_t tagged constructor, or a constructor taking a pair of iterators, or by inserting each element of the range into the default-constructed object.

ranges​::​to is applied recursively, allowing the conversion of a range of ranges.

Let reservable-container be defined as follows: template<class Container> constexpr bool reservable-container = // exposition only sized_range<Container> && requires(Container& c, range_size_t<Container> n) { c.reserve(n); { c.capacity() } -> same_as<decltype(n)>; { c.max_size() } -> same_as<decltype(n)>; };

Let container-insertable be defined as follows: template<class Container, class Ref> constexpr bool container-insertable = // exposition only requires(Container& c, Ref&& ref) { requires (requires { c.push_back(std::forward<Ref>(ref)); } || requires { c.insert(c.end(), std::forward<Ref>(ref)); }); };

Let container-inserter be defined as follows: template<class Ref, class Container> constexpr auto container-inserter(Container& c) { // exposition only if constexpr (requires { c.push_back(declval<Ref>()); }) return back_inserter(c); else return inserter(c, c.end()); }