Reverse range adapter

[Pete Cooper]

Once more update.  Seems I hadn’t handled pointers.  Added a variant which takes a pointer to a container and calls ->rbegin() and ->rend().


> On Jul 28, 2015, at 10:19 AM, Pete Cooper <peter_cooper at apple.com> wrote:
> 
>> 
>> On Jul 28, 2015, at 9:59 AM, David Blaikie <dblaikie at gmail.com <mailto:dblaikie at gmail.com>> wrote:
>> 
>> I'm OK calling it 'reverse' as you have (since it has just the one argument it shouldn't be ambiguous with the iterator versions)
>> 
>> * These functions shouldn't be ‘static’
> Good point.  Made them inline like the other methods in the same file.
>> * Could you try using non-member begin/end in the second version - that should allow it to work with arrays. Give it a go/add a test?
> Done.  Added a test for this too.
>> * Maybe test the case where a container has rbegin/rend and begin/end to ensure we still favor the rbegin/rend (and that it's not ambiguous?) - presumably they're more efficient, if they're provided?
> Added a test for this too.  I left begin(), end() without method bodies so that if they were called we’d get linker errors.
>> 
>> & the reason you don't need explicit SFINAE is because you put the interesting expressions in the return type - so they're part of the SFINAE condition already, conveniently.
> Makes sense.  Thanks for the explanation.
>> 
>> I think Saleem (cc'd) had an existing implementation of something like this that he might be willing to provide some insight from?
> Cool.  Happy to see his implementation too, and to take whichever suits.
> 
> Updated patch included.
> 
> Cheers,
> Pete
> 
> <reverse.patch>
> 
>> 
>> On Tue, Jul 28, 2015 at 9:43 AM, Pete Cooper <peter_cooper at apple.com <mailto:peter_cooper at apple.com>> wrote:
>> Hi David
>> 
>> Please find attached a patch for a reverse range adapter.  Its based on feedback you gave in http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20150720/289410.html <http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20150720/289410.html>.
>> 
>> There are 2 versions.  The first uses rbegin()/rend(), the second constructs std::reverse_iterators around begin()/end().
>> 
>> I was surprised to find I didn’t need enable_if or any other such tricks.
>> 
>> I’ve updated a single use of the pattern ‘for auto x : make_range(rbegin(), rend())’ to the new reverse method.
>> 
>> I was considering reverse_range instead as a name to avoid confusion with std::reverse.  I’d prefer to not do make_reverse_range just to save on characters.
>> 
>> Feedback welcome.
>> 
>> Cheers,
>> Pete
>> 
>> 
>> 
>> 
> 
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