It was short for the explanation in the following paragraphs (OK I should have added "without unwanted storage side effects" which was the whole point though).

It was short for the explanation in the following paragraphs (OK I should have added "without unwanted storage side effects" which was the whole point though). WHich I still haven't seen resolved in a memorable/non-gross way (I do assume extempore's hack works). Even Martin's private[this] idea from that thread was apparently never implemented, I just tried it also. I'm a Scala fan by the way, and this is a solvable problem (the private[this] solution would be fine I think). But it's currently a landmine IMO and an unfortunate because it's such an unforced error.