|Category: functors||Component type: concept|
|Argument type||F::argument_type||The type of F's argument|
|Result type||F::result_type||The type returned when the Unary Function is called|
|F||A type that is a model of Unary Function|
 Note the implication of this: a function pointer T (*f)(X) is a Unary Function, but not an Adaptable Unary Function: the expressions f::argument_type and f::result_type are nonsensical.
 When you define a class that is a model of Adaptable Unary Function, you must provide these typedefs. The easiest way to do this is to derive the class from the base class unary_function. This is an empty class, with no member functions or member variables; the only reason it exists is to make defining Adaptable Unary Functions more convenient. Unary_function is very similar to the base classes used by the iterator tag functions.