Hi Joaquin,
Starting with Boost 1.35, Boost.MultiIndex ordered indices guarantee that hinted insertion takes place as close as possible to the hint, please take a look at http://www.boost.org/libs/multi_index/doc/release_notes.html#boost_1_35 . But what means "as close as possible"? Is "before the hint" closer then "after the hint" by definition? I doubt it. DR233 and the resolution isn't more clear in that respect too and I'm going to raise the question in csc++ if I don't find a clarification elsewhere. boost::intrusive has introduced insert_before (@Ion: the function is nowhere stated in the release notes for 1.41 but I didn't found it in 1.40), which does exactly what I need. However using boost::intrusive is somewhat more difficult (even if for a particular reason I know how to use it ;-)
But you're right this is not stated in the docs. I'll change that. It'd help if you can file a ticket for the issue so that I don't forget. I'll do that.
Best regards Olaf