Wow, there's a G code standard that states that expressiions like #1 = [-#2] aren't legal?
I've reported that as bug in Mach several times over the past couple of years and I thought it just never made it high enough up on the priority to get fixed, I didn't know there was actually a spec somewhere saying it shouldn't be legal.
Having to do #1=[0 - #2] sure makes macros look ugly, I'd be really surprised of most of the modern CNC controllers (Fanuc, Haas, Fadal, Siemens, etc.) still adhered to that part of the spec.
Paul T.