hi, I would like to ask if there is a way boost::preprocessor may be used to solve the following problem: The problem is to define a macro that expands to the concatenation of their arguments, without duplicates. The arguments are symbols belonging to a known alphabet. For example, one possible solution for a macro which can take 3 symbols from the alphabet (A,B,C), would be #define RemoveDuplicates(S1,S2,S3) S1 ## S2 ## S3 #define AAA A #define AAB AB #define ABA AB #define ABB AB #define BAA AB #define BAB AB #define BBA AB #define BBB B In my real problem I have an alphabet of 10 symbols, which would be solved similarly with 10^10 #defines instructions, which is too much for the c++ preprocessor. So finally, is there any way boost::preprocessor can help me on this? And also, is there any paper or other document explaining how does boost::preprocessor works inside ? thanks Marco -- Marco Correia