Man Page unary_function.3

                       Standard C++ Library
             Copyright 1998, Rogue Wave Software, Inc.



      - A base class for creating unary function objects.


     #include <functional>
     template <class Arg, class Result>
     struct unary_function{
      typedef Arg argument_type;
      typedef Result result_type;


     Function objects are objects  with  an  operator()  defined.
     They  are  important  for  the effective use of the standard
     library's generic algorithms, because the interface for each
     algorithmic  template  can  accept  either an object with an
     operator() defined or a pointer to a function. The  standard
     library includes both a standard set of function objects and
     a pair of classes that you can use as the base for  creating
     your own function objects.

     Function objects that take one  argument  are  called  unary
     function  objects.  Unary  function  objects are required to
     include the  typedefs  argument_type  and  result_type.  The
     unary_function  class makes the task of creating templatized
     unary function objects easier  by  providing  the  necessary
     typedefs  for  a  unary function object. You can create your
     own   unary   function   objects    by    inheriting    from


     Function_Objects, and Function  Objects  Section  in  User's