A Functor that deletes Pointers from STL Sequence Containers

/*
Copyright (c) 2004, Nemanja Trifunovic
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

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this list of conditions and the following disclaimer. 

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this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.

The name of Nemanja Trifunovic may not be used to endorse or promote products
derived from this software without specific prior written permission. 

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
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*/

#if !defined FREE_PTR_POLICY
#define FREE_PTR_POLICY


#include <cstdlib>      // free()
#include <functional>   // unary_function

namespace FreePtr
{
// Cleanup policies: do we use delete, delete[], or free() to delete objects?
struct DeleteSingleObject
    {
    template <typename T> static void Destroy(T* ptr)
        {
        delete ptr;
        }
    };

struct DeleteArray
        {
    template <typename T> static void Destroy(T* ptr)
        {
        delete[] ptr;
        }
    };

struct Free
        {
    template <typename T> static void Destroy(T* ptr)
        {
        std::free (ptr);
        }
    };

// Zero Pointer policies: Do we set deleted pointer to zero, or not?
struct DontZeroPtr
    {
    template <typename T> static void Zero(T*& ptr)
        {}
    };

struct ZeroPtr
    {
    template <typename T> static void Zero(T*& ptr)
        {
        ptr = 0;
        }
    };

// The real thing: a functor to delete pointers from a sequence. 
template <typename T, class CleanUpPolicy = DeleteSingleObject, class ZeroPtrPolicy = DontZeroPtr>
struct free_ptr : std::unary_function <T*, void>
    {
    void operator()(T*& ptr)
        {
        CleanUpPolicy::Destroy(ptr);
        ZeroPtrPolicy::Zero(ptr);
        }
    };
    
}// namespace FreePtr
#endif