=====for_each=====
Syntax:

<code>
    #include <algorithm>
    UnaryFunction for_each( input_iterator start, input_iterator end, UnaryFunction f );
</code>

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:

<code>
   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;
</code>

The above code displays the following output:

<code terminal>
   Before, nums[] is: 3 4 2 9 15 267
   After, nums[] is: 4 5 3 10 16 268
</code>