"Keith MacDonald"
You have proposed a very elegant solution, but I would defy anyone who does not understand the library inside out to arrive at that solution. The documentation (iterator/doc/index.html#iterator-facade-and-adaptor) states:
We're working on the docs. That document is the standards proposal, but the Boost (user-level) docs aren't complete yet.
"It is common to define a new iterator which behaves like another iterator, but which modifies some aspect of its behavior. For that purpose, the library supplies the iterator_adaptor class template, which is specially designed to take advantage of as much of the underlying iterator's behavior as possible."
In this case, I can't see what the underlying iterator is, so don't understand how iteration can proceed.
I quote: The iterator_adaptor class template adapts some Base 3 type to create a new iterator. Instantiations of iterator_adaptor are derived from a corresponding instantiation of iterator_facade and implement the core behaviors in terms of the Base type. In essence, iterator_adaptor merely forwards all operations to an instance of the Base type, which it stores as a member. [3] The term "Base" here does not refer to a base class and is not meant to imply the use of derivation. We have followed the lead of the standard library, which provides a base() function to access the underlying iterator object of a reverse_iterator adaptor. The user of iterator_adaptor creates a class derived from an instantiation of iterator_adaptor and then selectively redefines some of the core member functions described in the table above. The Base type need not meet the full requirements for an iterator. It ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ need only support the operations used by the core interface functions of iterator_adaptor that have not been redefined in the user's derived class.
For example, if you add the statement "++x;" to your example, it fails to compile.
Umm, sorry. I whipped that one off without too much testing. I've enclosed a fixed one.
To return to my point about the purpose of a software library, my approach is generally to ask if it will allow me to implement code more quickly and reliably than without it. I got to the point of thinking, I've now got to implement a straightforward iterator, sigh, so will the boost library help me? I didn't expect to have to develop a deep understanding of template metaprogramming and the curiously recurring template pattern, before I could move on.
Why would you need to develop either of those? You just follow the formula.
Hence my plea for an example of a plain vanilla iterator, by which I meant something similar to those used for the std library containers.
I'm sorry, I need you to be more specific. Is the example of your node iterator good enough? -- Dave Abrahams Boost Consulting www.boost-consulting.com