Lathe ball-end multi-pass subroutine

I didn't really find a subroutine to make a multi-pass ball end to a given stock diameter with the ball radius as a parameter, so I tried to make one up for myself. It is based on the od-taper multipass routine and uses some juggling with the circle equation. You can toggle the tool diameter compensation with the "skip lines" option. The tool diameter parameter is only needed for the exit move. It could be fixed to the largest tool diameter used which then results in a larger +Z exit movement than needed. I do not know of a way to extract the tool diameter in a subroutine, but maybe there is one. I am rather new to tool radius compensation on a lathe, so I may have done the entry and exit moves in a weird way. I only used metric (G21) mode on a machinekit version of linuxcnc and I have not cut any metal with it, so be careful when trying it out. I would appreciate any comments or hints to a different way of making a ball end.
Karl
EDIT: just found out about #5410 being the tool diameter, new version attached.
EDIT2: had the #5410 statement at the wrong position (before loading tool), corrected version attached

I added spring passes and refined the code somewhat to avoid strange entry moves for tool compensation with very small tool diameters. The new version is in the first post.
Karl