what would you say to this: namespace rational { template < class unlimited > class unlimited { //... } ; enum policy { round , round_and_exactness , exception , assert } ; // for power users template < typename limited , policy rounding = round > class fxs_ { //... } ; typedef __int64 biggest_builtin ; // for end-users template < biggest_builtin limit = INT_MAX , policy rounding = round > class fxs : public fxs_< fastest type that can hold [-limit...limit] , rounding > { //... } ; // if you are really desperate and want to specify by hand // the num_type, den_type, num_min, num_max, den_min, den_max etc // there is a way to create your own policy blob // of course we need better names than fxs and fxs_ } br, andras