>(A) Sounds like you're describing an LRU.

Sounds the same but are different, i know what an LRU and I'm not describing it, 

LRU involves two separate containers,  my proposal suggest a tweak on std::unordered_set. 

>(B) You're talking to the wrong list here. Step >1 is for you to want this data structure for >some actual reason (not just that you just >learned about it, but that you have a real >place to use it in your own code). Step 2 is for >you to implement it in code. (Put it on GitHub >or something.) Step 3 is to stop there, since >once the code is available there's no reason >to bother the Committee with it; but at least >there's certainly no sense in bothering the >Committee with it before steps 1 and 2 have >happened.

That was rude for my taste... but hey...everyone has his way of expression and i respect it,  and modesty is a virtue.

I think i will take your advice and push my code to gitHub, that's better.

>(C) Have you looked at what you'd get by >using Boost.MultiIndex?  (Search "boost >multiindex lru" to find people already using it >as an LRU.)

I will.