std::format_kind
Min standard notice:
Header: <format>
The variable template format_kind selects an appropriate std::range_format for a range R.
# Declarations
template< class R >
constexpr /* unspecified */ format_kind = /* unspecified */;
(since C++23)
template< ranges::input_range R >
requires std::same_as<R, std::remove_cvref_t<R>>
constexpr range_format format_kind<R> = /* see description */;
(since C++23)
# Example
#include <filesystem>
#include <format>
#include <map>
#include <set>
#include <vector>
struct A {};
static_assert(std::format_kind<std::vector<int>> == std::range_format::sequence);
static_assert(std::format_kind<std::map<int>> == std::range_format::map);
static_assert(std::format_kind<std::set<int>> == std::range_format::set);
static_assert(std::format_kind<std::filesystem::path> == std::range_format::disabled);
// ill-formed:
// static_assert(std::format_kind<A> == std::range_format::disabled);
int main() {}