unary_function

     Function Object

Base class for creating unary function objects.

Contents

• Synopsis
• Description
• See Also

#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 provides 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 provide the typedefs argument_type and result_type. The unary_function class makes the task of creating templated 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 unary_function.

Function Objects, and Function Objects Section in User's Guide.