for_each

     Algorithm

Applies a function to each element in a range.

Contents

• Synopsis
• Description
• Complexity
• Example
• Warning
• See Also

#include <algorithm>

template <class InputIterator, class Function>
 void for_each(InputIterator first, InputIterator last,
               Function f);

The for_each algorithm applies function f to all members of the sequence in the range [first, last), where first and last are iterators that define the sequence. Since this a non-mutating algorithm, the function f cannot make any modifications to the sequence, but it can achieve results through side effects (such as copying or printing). If f returns a result, the result is ignored.

The function f is applied exactly last - first times.

//
// for_each.cpp 
//
#include <vector>
#include <algorithm>
#include <iostream.h>
 // Function class that outputs its argument times x
 template <class Arg>
 class out_times_x :  private unary_function<Arg,void>
 {
   private:
      Arg multiplier;
   public:
      out_times_x(const Arg& x) : multiplier(x) { }
      void operator()(const Arg& x) 
         { cout << x * multiplier << " " << endl; }
 };
 int main()
 {
   int sequence[5] = {1,2,3,4,5};  
   // Set up a vector
   vector<int> v(sequence,sequence + 5);
   
   // Setup a function object 
   out_times_x<int> f2(2);
   for_each(v.begin(),v.end(),f2);   // Apply function
   return 0;
 }
Output : 2 4 6 8 10

If your compiler does not support default template parameters then you need to always supply the Allocator template argument. For instance you'll have to write:

vector<int, allocator>

instead of:

vector<int>

Algorithms, Function Objects