std::experimental::in_place
Min standard notice:
Header: <experimental/optional>
std::experimental::in_place is a constant of type std::experimental::in_place_t that is used to disambiguate the overloads of constructors and member functions of that take arguments (possibly a parameter pack) for in-place construction of some value.
# Declarations
constexpr in_place_t in_place{};
(library fundamentals TS)