On Sat, Oct 30, 2010 at 6:28 PM, Robert Jones <robertgbjones@gmail.com>wrote:
On Sat, Oct 30, 2010 at 12:38 PM, Neil Groves <neil@grovescomputing.com
wrote:
I propose that a breaking change is made to the index range adaptor so
that
it returns a pair<original_reference_type, index_type>.
Hi Neil
Could you provide a use-case example, before and after.
Certainly. I should have thought to do this in the original email. Thank you for taking the time to help me acquire information. Before: BOOST_FOREACH( auto item, rng | index ) { // access to the index is not possible - doh :-( // The return type of the dereferenced element from an index range adaptor loses the index const element_type& elem = item; } After: BOOST_FOREACH( auto item, rng | indexed ) { // After my proposed modification, the return type becomes a pair of the index // and the original reference type of the underlying iterator/range. std::size i = item.first; const element_type& elem = item.second; }
Thx - Rob.
I hope this makes the motivation for the change clearer. My original design does, of course, work if one writes the algorithm specifically to extract the index directly from the iterator. This is unnecessarily limiting. Regards, Neil Groves