Suppose you have a Widget class that supports redrawing:

class Widget
{
public:
    Widget();
    virtual ~Widget();
    void redraw() const;
};

and you'd like to redraw all the Widgets in a list, you could do it within a loop:

list<Widget> lw;
// ...
for (list<Widget>::iterator i = lw.begin(); i != lw.end(); ++i)
{
    i->redraw();
}

But you could also do it with the for_each algorithm:

for_each(lw.begin(), lw.end(), mem_fun_ref(&Widget::redraw));

Why should we prefer algorithm to writing our own loop? Here are the reasons:

• Efficiency:
  Algorithms are offten more efficient than the loops programmers produce.
• Correctness:
  writing loops is more suject to errors than is calling algorithms.
• maintainability:
  Algorithm calls often yield code that is clear and more straightforward than the corresponding explicit loops.