Anthony Williams <anthony_w.geo@yahoo.com> writes:
I am somehow failing to communicate the design to you; it may be best for you to look at the code, or read my article on the original pair-based implementation (http://web.onetel.com/~anthony_w/cplusplus/pair_iterators.pdf)
I worked hard on this to ensure it met all the requirements of the various iterator categories. I am disturbed that I missed the requirement about == implying the same object, but please do not assume that other requirements are not met unless you have direct evidence.
I wasn't assuming; I was just wrong ;-)
operator* returns a real reference to an object stored within the iterator. This object is a tuple of references to the objects returned by dereferencing the source iterators, with some custom behaviour to handle copying.
This custom behaviour means that copies of this tuple actually hold copies of the originally-referenced data, and the references on this new copy point back within itself to the copies of the data.
That is evil and sneaky! I love it! Thanks for the explanation. Is that object the same as the iterator's value_type? If so, I don't see how swap(*i1, *i2) can work, and thus most sort implementations should fail. If not, it's not conforming in another way because operator* must be a reference to value_type. Have I missed something else? -- Dave Abrahams Boost Consulting http://www.boost-consulting.com