In message , at
00:50:46 on Sat, 18 Feb 2012, Neil Williams
remarked:
There is the similar barber shop variant, in which you are expected to
work out who is before you without a visible queue or asking.

No, you don't need to know anything about the people who arrived before
you. All that's necessary is to know is that of all the people still
waiting, you were first to arrive (and therefore saw all the others
arrive after you).

The same is true at pubs where the staff are too incompetent to note the
order of arrivals, and ask the customers "who is next".
--
Roland Perry