However, boost's zip_iterators are not writable. I don't really think it would be possible to make them writable, but that would allow code like this:
<snip> </snip>
template
auto join(C&& c, D&& d, Args&&... args) -> decltype(boost::join(boost::join(boost::make_iterator_range(std::forward<C>(c)),
boost::make_iterator_range(std::forward<D>(d))), join(std::forward<Args>(args)...))) { return boost::join(boost::join(boost::make_iterator_range(std::forward<C>(c)),
boost::make_iterator_range(std::forward<D>(d))), join(std::forward<Args>(args)...)); }
A variadic zip is more complicated. If we want write access we cannot use boost zip_iterator. Still one can use Anthony Williams' TupleIterator:
template
auto zip(T&&... c) -> boost::iterator_range< decltype(iterators::makeTupleIterator(std::begin(std::forward<T>(c))...))> { return boost::make_iterator_range (iterators::makeTupleIterator(std::begin(std::forward<T>(c))...), iterators::makeTupleIterator(std::end(std::forward<T>(c))...)); }
For read-only access one could use boost::zip_iterator, but I think write-access is _really_ important (e.g. sort wouldn't work).
Would it be possible to add similar functionality to boost range?
Yes and I shall do so when I find time. If you find time to create a patch it would be even quicker of course, but I understand if this is not possible. It seems we are all running with less and less time to work on these extra-curricula projects!
This code wouldn't work without the help of everyone who participated in the following SO discussions: -
http://stackoverflow.com/questions/14366576/boostrangejoin-for-multiple-rang... -
http://stackoverflow.com/questions/13840998/sorting-zipped-locked-containers... and without Anthony Williams's tupleIterator. See also http://www.justsoftwaresolutions.co.uk/articles/pair_iterators.pdf
I'll have to see if I can persuade Anthony to be charitable enough to allow us to include his tuple iterator. Ideally this would be made a public feature of Boost.Iterator I think.
Bests, Gonzalo BG
Thank you for your feedback. It's great to have positive suggestions that are actionable like this. Regards, Neil Groves