On Fri, 20 Dec 2019 at 10:30, Klaus Doldinger <klaus.doldinger64@xxxxxxxxx> wrote: > Am 20.12.19 um 11:25 schrieb Jonathan Wakely: > > On Fri, 20 Dec 2019, 08:39 Klaus Doldinger, <klaus.doldinger64@xxxxxxxxx> wrote: > >> But, how do I write a class to use as NTTP with private members? > > > > > > You don't. > > Well, that is an extremly hard restriction, I think. > Are there reasons for that? Several. In short, they don't work very well and introduce inconsistencies and warts to the language. http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1837r0.html covers some of it.