Dear All, I've written a set of classes. Suppose I have a class called WorkCenter and another called Machine. I created a smart pointer to each Machine object. Each Workcenter has one or more Machines. I could create a vector of MachineSmartPointers. But I will need to search for Machines by some different index keys, like by the unique ID (an Int) or by Tag (a String). I could not find any example like that. In the Boost documentation the example is made with a struct. I know that a class, in C++, is very similar to a Struct. But I dont know how to write this code. Could someone give me a light on this? Thanks in advance. -- sds. Written by - Escrito por: José Augusto M. Andrade Jr. - JamaJ