I think perhaps the cryptic (aren't they all?) "exercise" in the "objects,
properties and attributes" (chap. 3) The example given is to detect of an
object has a door_to property. It reads:
if (obj.&door_to == 0) then {. . .}
The & symbol is saying that you want to know the address of the door_to
property. So i assume what's happening in this example (there is no
explanation given in the manual!) is that if there is no property then it
will return 0, hence you have detected that it has no door_to property in
this case.
Someone will have to correct me if I'm wrong.
--- ....with love and squalor. <as544@torfree.net>