...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Return true
if
this is a bool.
bool is_bool() const noexcept;
This function is used to determine if the underlying representation is a certain kind.
return this->kind() == kind::bool_;
Constant.
No-throw guarantee.