...one of the most highly
regarded and expertly designed C++ library projects in the
world. — Herb Sutter and Andrei
A special type, similar to std::nothrow_t, used to disambiguate constructors that accept executor arguments.
struct is an empty structure type used as a unique type to disambiguate constructor
and function overloading. Specifically, some types have constructors with
as the first argument, immediately followed by an argument of a type that
satisfies the Executor type requirements.