namespace std {
class future_error : public logic_error {
public:
future_error(error_code ec); // exposition only
const error_code& code() const noexcept;
const char* what() const noexcept;
};
}
const error_code& code() const noexcept;
Returns: The value of ec that was passed to the object's constructor.
const char* what() const noexcept;
Returns: An ntbs incorporating code().message().