Simple iterator adaptor example

I have taken a quick look at iterator adaptor and it seems quite powerful. It seems that iterator_adaptor has two uses. First to adapt one iterator to another. It also seems like it should be able to be used as an interface to other information that has container like qualities that needs an iterator. For example files in directory. Does anyone have an example of how to build one of the later? Not specifically an iterator over files, but the general ability to build an iterator from something that's not an iterator? Thanks for the pointers, ..Duane