在STL中使用比较算法

Question

I am reading about algorithms at following location.

http://www.brpreiss.com/books/opus4/html/page116.html

Here it is mentioned as below

template <class T>
int Wrapper<T>::CompareTo (Object const& obj) const
{
    Wrapper<T> const& arg =
    dynamic_cast<Wrapper<T> const&> (obj);
    return ::Compare (datum, arg.datum);
}

The CompareTo member function is implemented in the same way as the Hash member function. Ie, it calls the global (non-member) function ::Compare to do the actual comparison.

My question; what does author mean by global compare function in C++? Do we have to include any header file here as code is not compiling?

Answer 1

As one of the comment mentioned above here in this context Compare is nothing to do with STL. I missed the last sentence on the page: "The implementation of a suitable compare function is left as a project for the reader"