This library is useful as is but I would suggest a few additional features for convenience especially among the most common use cases. 1) convenience functions preferably, documented example is acceptable, for extracting a integer, int, long int ... starting at a particular unsigned bit offset for a particular length 2) convenience functions preferably, documented example is acceptable, for creating a mask starting at a particular unsigned bit offset for a particular length 3) examples of using this if possible with boost::date in order to efficient work with dates outside the existing limits 4) conversion to and from dynamic_bitset [already suggested just seconding] 5) conversion to and from bitset For all those other reviewers who may complain about performance when comparing with GMP, please bear in mind that large numbers are useful to domains other than security were assembly level performance is nice but doesn't outweigh other concerns such as portability and ease of use. This library and others much needed even overdue for the C++ non C community.