In a recent project I've been working on, we had need for something that I'm calling (for lack of a better, more inspired name ;) an 'indexed' multi array. Essentially, we wanted something like a boost multi_array but that also allowed indexing along each dimension using some kind of indexing function. For example, along one dimension the indexing function may except a string as input and use a map to return an integer index, while along some other dimension the real line may be cut into non-overlapping intervals and a double value is looked up returning the index of the interval it belongs to. We looked at various solutions, but in the end rolled our own based off of the boost multi_array and a new concept of an 'indexer'. Is this something that anybody else would see as useful? I hope my explanation was sufficiently clear ;) Cheers, Chris Hamilton