On Fri, May 8, 2009 at 1:38 PM, Jeremiah Willcock <jewillco@osl.iu.edu>wrote:
Theoretically, anything that can be iterated and swapped can be sorted. Do
you have a genuine usage case where a sort would be useful where an item can be iterated and swapped, but does not have a Random Access Iterator? If so, I could reconsider the request and see if I can find (or write) an effective algorithm and template it.
Yes, I do -- the case of sorting two (or more) corresponding sequences using a zip_iterator. This capability is important to save memory when explicitly zipping the sequences into a new sequence is not possible. Note that zip_iterator still has random access in constant time, but just does not return an actual reference but a tuple of references.
so if I (theoretically) were to use ++ to iterate over the array, calling std::swap(element_position, correct_position), then the zip_iterators would be sorted correctly? Can I use -- (Is it bidirectional)? That would improve runtime. I would expect begin() and end() to be passed in as the arguments to the sort method. If so, please send me a testcase you expect to work, and I can try to find an appropriate algorithm, and template it (Quicksort would work, but it's O(n*n)).