|  | 
The type of the function's argument.
typedef see_below argument_type;
          The type of argument_type
          is based on the type T
          of the wrapper's target object:
        
T is a pointer to
              a function type accepting a single argument, argument_type
              is a synonym for the return type of T;
            T is a class type
              with a member type argument_type,
              then argument_type
              is a synonym for T::argument_type;
            argument_type
              is not defined.
            
          Header: asio/bind_immediate_executor.hpp
        
          Convenience header: asio.hpp