[Boost-users] Re: boost::iterator_facade problem with postfix increment proxy

David Abrahams wrote:

Jens Theisen writes:

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My reference type is a simple reference, I want to implement an lvalue iterator (at least in some cases).

And why is it only single-pass?

...

I am trying to make a proxy iterator

^^^^^^^^^^^^^^ What do you mean by that?

It is a class templated on a value_type to with implementations can be attached (at run time). For example: List< char > l = makeList(some_std_string) + makeList(some_char_array); l.begin(), l.end() give you an iterator which type depends solely on the value_type (char in this case), rather than the iterator types used as backends (std::string::iterator and pointers). These iterators will iterate over the std::string first and after this over the char array.

I don't see why that would be incompatible with forward traversal. We don't even seem to have a requirement that a copy of an iterator compares equal with it. Perhaps we should; then you might be in trouble [Jeremy, Thomas, your thoughts?]

Oh, you're right. I somehow assumed that would be the case. However, this is a requirement for Forward iterators, and iterator_faced gives the forward_traversal_tag to Forward traversal iterators with reference reference type. So it maybe a good idea to add this requirement.

That shouldn't be slow if there's plenty of inlining.

The indirections are runtime indirections. Best regards, Jens