In this chapter, we focused on containers specialized for looking up objects based on multiple criteria. Specifically, we looked at Boost Bimap which is a bidirectional map object, whose keys and values can both be looked up efficiently. We also looked at Boost Multi-index containers, which are generic associative containers with multiple associated indexes, each assisting the efficient look up of an object on one criterion.

In the next chapter, we change gears to look at functional composition and metaprogramming techniques that enable us to write powerful and expressive applications with excellent runtime performance.