#include <algorithm>
  UnaryFunction for_each( iterator start, iterator end, UnaryFunction f );

The for_each() algorithm applies the function f to each of the elements between start and end. The return value of for_each() is f.

For example, the following code snippets define a unary function then use it to increment all of the elements of an array:

 template<class TYPE> struct increment : public unary_function<TYPE, void> {
   void operator() (TYPE& x) {
     x++;
   }
 };             

 ...            

 int nums[] = {3, 4, 2, 9, 15, 267};
 const int N = 6;               

 cout << "Before, nums[] is: ";
 for( int i = 0; i < N; i++ ) {
   cout << nums[i] << " ";
 }
 cout << endl;            

 for_each( nums, nums + N, increment<int>() );            

 cout << "After, nums[] is: ";
 for( int i = 0; i < N; i++ ) {
   cout << nums[i] << " ";
 }
 cout << endl;            

The above code displays the following output:

 Before, nums[] is: 3 4 2 9 15 267
 After, nums[] is: 4 5 3 10 16 268