Re: templated deletePointer in for_each algorithm

"Kaz Kylheku" <>
8 Jun 2006 16:45:41 -0700
shaun wrote:


//Now: how to delete a map of pointers using for_each?

By defining a functor which binds the function to the pair->second.

First, write this class:

template <class PAIR>
class take_second {
  typedef void (*func_type)(typename PAIR::second_type &);
  func_type func;
  take_second(func_type f) : func(f) { }
  void operator()(PAIR &p)

Now, you can do this:

   for_each(myMap.begin(), myMap.end(),
            take_second<map<int, string

The third argument of for_each here constructs a temporary object of
type take_second<T> where T is the pair<const int, string *> (the
value_type of the map). As a constructor argument, the deletePointer
function is passed. The functor remembers that function. The for_each
function calls the functor for every pair<> in the map, and the
functor, in turn, selects the second member of the pair and invokes the
remembered function on it.

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