hello, technically, this is not a boost question. I am writing a library to be used by third-party developers. Internally, i use boost::mpl sequences. Joaquin wrote mpl sequences cross-product metafunctions that i use, i called them sequence2_cross_product and sequence3_cross_product for the x-product of 2 and 3 sequences. I put the metafunction in a separate header file. I don't intend to expose it to my clients. Is there an agreed convention/style as to where such a header file should lie? My namespace hierarchy reflects my directory structure, so this is like asking in which namespace should i put this metafunction. I would have like to see such metafunctions already in boost::mpl., so should/can i highjack boost::mpl namespace in my header? or put it at toplevel right below my namespace ? rds,