boost::random::traits::make_unsigned_or_unbounded — Converts the argument type T to either an unsigned type or an unbounded integer type.
This trait has a single member `type` which is either the unsigned type corresponding to T or an unbounded integer type. This trait is used to generate types suitable for the calculation of a range: as a result if T is signed, then member `type` *should define a type with one more bit precision than T*. For built-in types this trait defaults to `boost::make_unsigned<T>::type`. For user defined types it simply asserts that the argument type T is either an unbounded integer, or an unsigned one (using std::numeric_limits). User defined specializations may be provided for other cases.