+{
+ ::std::string m_str;
+public:
+ explicit str_except(const string& what_arg);
+ virtual ~str_except() noexcept;
+ str_except& operator= (const str_except& e) noexcept;
+ virtual const char* what() const noexcept;
+};
+
+} // namespace _bits
+
+class logic_error:
+ public _bits::str_except