Grammar allows zero

[timbrisc]

Issue migrated from trac ticket # 172

component: help | priority: minor | keywords: semantics, grammar

2015-04-28 03:31:41: dmcclean created the issue

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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 , and therefore as a .

It shouldn't be permitted as a 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."