I intended to comment on the discussion related to "Clipped Objects" but the thread has been closed.
In order to place an object down and have it be clipped, you need to use the plot command. So what happens when you want to set and object down (an arrow, box, polygon, or point) and you want to use expressions that incorporate variables like pi or other user-defined functions?
So far the answer is...
plot '-' u (expr1):(expr2) w p
or the suspicious (i.e., I can't assume this works on all systems)
plot '< echo "0 0 0 0 0 0 0"' u (expr1):(expr2) w p
As the plot commands become more elaborate, I find myself creating tons of dummy inline data files so that I can just use an expression to put these elements down. I wish this were easier. For instance, I wish there was something like
plot 'dummy' u (expr1):(expr2) w p
Am I missing something? Any suggestions?