namespace ThirdPartyLib
{
template <typename T>
class SomeContainerFromAThirdPartyLib
{
public:
typedef T ValueType; // not value_type!
// no difference_type
class iterator
{
public:
typedef T ValueType; // not value_type!
// no difference_type
// obviously this is not how these would actually be implemented
int operator != (const iterator& rhs) { return 0; }
iterator& operator ++ () { return *this; }
T operator * () { return T(); }
};
// obviously this is not how these would actually be implemented
iterator begin() { return iterator(); }
iterator end() { return iterator(); }
};
}
#include <cstddef>
#include <iterator>
namespace MyLib
{
template <typename T>
class iterator_adapter : public T
{
public:
// replace the following with the appropriate types for the third party iterator
typedef typename T::ValueType value_type;
typedef std::ptrdiff_t difference_type;
typedef typename T::ValueType* pointer;
typedef typename T::ValueType& reference;
typedef std::input_iterator_tag iterator_category;
explicit iterator_adapter(T t) : T(t) {}
};
template <typename T>
class iterator_adapter<T*>
{
};
}
#include <iostream>
#include <algorithm>
using std::cout;
using std::endl;
template <typename iter>
typename MyLib::iterator_adapter<iter>::difference_type
count(iter begin, iter end, const typename iter::ValueType& val)
{
cout << "[in adapter version of count]";
return std::count(MyLib::iterator_adapter<iter>(begin), MyLib::iterator_adapter<iter>(end), val);
}
using std::count;
int main()
{
char a[] = "Hello, world";
cout << "a=" << a << std::endl;
cout << "count(a, a + sizeof(a), 'l')=" << count(a, a + sizeof(a), 'l') << endl;
ThirdPartyLib::SomeContainerFromAThirdPartyLib<int> container;
cout << "count(container.begin(), container.end(), 0)=";
cout << count(container.begin(), container.end(), 0) << endl;
return 0;
}