[Question] nesting prefixes

[triallax]

From the types of "prefix" functions (e.g. mega) it seems like I can "nest" prefixes like so: kilo (mega gram). Is this intended, and if not, are there any safeguards against that?

[sharkdp]

Thank you for reporting this.

I think you are right. Nesting itself wouldn't be too bad (IMO), but I think the result would be that of the outer prefix instead of a proper composition/multiplication of the prefixes. Example:

• I think it would be okay if kilo (mega gram) == giga gram. Similar constructions come up if you have something like 1 kW / g * 1 kg = 1 "kilo kilo" W = 1 MW
• I would say that we should fix something if currently kilo (mega gram) == kilo gram.
• Completely preventing kilo (mega gram) would also be okay for me.

What do you think?

[triallax]

I definitely agree that if 2 is the case, it should be fixed. I also think that either 1 or 3 are fine, but I'm leaning towards disallowing it completely since I think it's very unlikely that one would be writing that on purpose and that it's likely to be a mistake (I welcome any invalidating examples). Of course, the expression you provided should still be possible to resolve to 1 MW, but one could also argue that 1000 kW is more "correct" in that it keeps the original prefix. That's a discussion for another day though, and if I'm not wrong this issue has no bearing on if it resolves to 1 MW or 1000 kW.

[sharkdp]

I just checked that (kilo (mega gram)) == (giga gram). I will add a test for that shortly. I think we could then close this ticket?

[triallax]

Yes, that sounds good to me.