> vague statements and half-truths Ouch! A bit offhand no? My choice was to cover N,Z,Q operationally -- as in what you can do with them. Everyone knows about

> vague statements and half-truths Ouch! A bit offhand no? My choice was to cover N,Z,Q operationally -- as in what you can do with them. Everyone knows about +,-,/ and so I think it makes sense to connect with this previous knowledge of the reader rather than get into the formality of sets and set containment. I stand by my choice.