[PATCH] D27874: ilist_iterator: Allow conversion between reverse and forward iterators

[Duncan P. N. Exon Smith via llvm-commits]

I think adding:
--
explicit iterator(reverse_iterator I) : I(++I.getReverse().base()) {}
explicit reverse_iterator(iterator I) : I(++I.getReverse().base()) {}
--
should fix the problem.
- getReverse() keeps the current semantics of getting the reverse of whatever you're currently referencing.
- conversions between forward/reverse do the same thing as std::reverse_iterator, with the off-by-1 thing.



> On 2017-Jan-30, at 09:43, David Blaikie <dblaikie at gmail.com> wrote:
> 
> Yeah, I think it might be too subtle to have these reverse iterators behave differently from other reverse iterators. (I haven't checked the spec in detail to see if it's only stD::reverse_iterator that has this oddity, or if all reverse iterators must do so) 'getReverse' seems like a good/clear solution, if a little odd but at least visibly so.
> 
> On Wed, Jan 25, 2017 at 3:33 PM Matthias Braun via Phabricator via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> MatzeB abandoned this revision.
> MatzeB added a comment.
> 
> I wasn't aware of the subtle shift-by-1 semantics when converting to std::reverse_iterator (must have missed the getReverse() comment). If we go with that semantics I would need extra std::next/std::prev calls in my code anyway which doesn't make it much simpler compared to MyIterator->getReverseIterator(). Going for semantics different from STL is not a good idea IMO.
> 
> 
> Repository:
>   rL LLVM
> 
> https://reviews.llvm.org/D27874
> 
> 
> 
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