Grammar allows zero
|Reported by:||dmcclean||Owned by:|
The UCUM 1.9 grammar (I'm not sure where to find any work-in-progress newer version, so I apologize if this has already been addressed) allows 0 to appear as a <digits>, and therefore as a <factor>.
It shouldn't be permitted as a <factor> because it doesn't have a multiplicative inverse. It's inclusion ruins the algebraic property noted in section 18 that "For each unit u ∈ U there is an inverse unit u-1 such that u · u-1 = 1. Thus, (U, ·) is an Abelian group."