Dana's implentation is wonderful but the Eureka accolade
must be for the simplicity and elegance of Tom Ogilvy's
intrinsic idea!

Indeed, and nicely expressed.
I can't help wonder if Tom might have allowed a wry
chuckle to himself at the notion he might be surprised by
the speed of this approach <vbg (earlier this thread).

implentation ?!!!
Should be implementation - I really was in a rush!

I really didn't notice until you corrected. Worrying - I
use the same eyes for reading my own code!

Peter