How do you get the 'pointed-to' type in C++?

template<typename T>
struct RemovePointer
{
    typedef T value_type;
};

template<typename T>
struct RemovePointer<T*>
{
    typedef typename RemovePointer<T>::value_type value_type;
};

What's the point? With a bit of boost magic, you can use pointers transparently in generic code:

#include <boost/bind.hpp>
#include <vector>
#include <list>
#include <algorithm>

struct Foo
{
    void f() const {}
};

template<typename T>
void doAll(const T& container)
{
    typedef typename
        RemovePointer<typename T::value_type>::value_type
            contained_type;

    std::for_each(container.begin(), container.end(),
            boost::mem_fn(&contained_type::f));
}

int main()
{
    std::vector<Foo*> fooPointers(4, new Foo);
    std::list<Foo> foos(4);
    doAll(fooPointers);
    doAll(foos);
} 

Now the generic function template doAll can be called on a container of Foos and a container of pointers to Foos, calling Foo::f() for each element.

Calling doAll for a container of pointers to pointers to Foos - such as std::vector<Foo**> - will cause a compile failure in boost::mem_fn.