Joaquin, list, In one of the last issues of the C/C++ User's Journal, Andrei Alexandrescu described the need for something better than std::map when using expensive keys: Let's start with two examples. The simplest one would involve the often-used map<string, something>: user names and user IDs, stock tickers and stock prices, class names and pointers to functions, words in Proust's opera and their counts...You can easily access the "something" if you have a key in the desired format. The problem is, you might have the key in a different format that forces a conversion. What if, for example, in your high-speed, high-availability, power-hungry, bonus-bringing stock market program, you have securities data come down the wire in raw char* format, but you need to look it up in a map<string, double>? More on http://www.ddj.com/dept/cpp/184402065 - might this be something boost::multi_index_container could be made to do? Not that boost::multi_index_container isn't wonderful enough already! Thanks. -- http://www.PowerDNS.com Open source, database driven DNS Software http://netherlabs.nl Open and Closed source services