Bug in logo like "arc" script

I'm trying to recreate the "arc" command from logo with angle and radius as input.
This works, but with a strange behavior:

When I try to move a negative radius the forward and backward paths aren't on top of each other. See here: https://snap.berkeley.edu/project?user=tbeatty&project=Logo%20Arc%20Bug

Thanks for the help!


Move radius/2 steps before the first turn and after the last turn.

Makes sense! Move then turn vs turn then move! Thanks!