boost::tuple has a get() member function used like this:
tuple<int, string, string> t(5, "foo", "bar");
cout << t.get<1>(); // outputs "foo"
It seems the C++0x std::tuple does not have this member function, and you have to instead use the non-member function form:
std::get<1>(t);
which to me looks uglier.
Is there any particular reason why std::tuple doesn't have the member function? Or is it just my implementation (GCC 4.4)?
The existing answers are great and certainly for the standards committee were vital for this purpose. But there is another issue that I think is important enough to mention.
With free functions, you have the ability to modify an interface without changing the definition of a class. You can make any type "gettable" simply by specializing the global get. With a member function, you would have to directly modify the class.
Range-based for looks for member begin/end on class types, but it also looks for non-member begin/end via ADL. These APIs can be used with any container, even those that don't have begin/end functions. You can specialize it for, for example, LibXML2 element types, such that you can range-based for over xmlElement*'s.
You can't do that if they had to be member functions.
In C++, free functions are a natural interface for many operations that could be done on many different kinds of classes.