-----Original Message----- From: boost-bounces@lists.boost.org on behalf of Peter Dimov I need to warn you that there is very little chance for your patch to be accepted in this form. Extending _bi::listN (I'd suggest making them conforming MPL or fusion sequences) needs to be done non-intrusively and in a separate header. ----- I understand what you mean here but didn't you say that the whole thing would be easier if one was to use a fusion tuple as L? I assumed that would have been the acceptable solution since you suggested that yourself. I would expect that making bind switch to tuple would be less work and more beneficial than introducing another sequence type (which I think is a lot more testing). FWIW, I'd be less interested in adding a new sequence type. Thanks for your reply. Sohail