"D'Arcy J.M. Cain" <darcy(at)druid(dot)net> writes:
> ... In fact, this seems to work already if
> quotes are added:
> box('(0, 1), (2, 3)')
Well, that's just another spelling for a box literal, which is exactly
what the OP *doesn't* want, since he's trying to construct a box value
from non-constant values.
regards, tom lane