Subject: Re: [xsl] () eq () vs () = () From: Andrew Welch <andrew.j.welch@xxxxxxxxx> Date: Mon, 3 Oct 2011 14:10:40 +0100 |
> It's a common misunderstanding about universal quantification. The > proposition > > every S satisfies P > > is always true when S is empty, regardless of P. > > For example, the statement "every hotel on St Kilda is fully booked" is > true, as is the statement "every hotel on St Kilda has vacancies" (there are > no hotels on St Kilda). Heh, nice. So: every hotel on St Kilda is fully booked, yet some hotel on St Kila isn't fully booked. In a potential summary then: () eq () returns () because... it's a special case where the atomisation of () returns () and not the empty string? () = () returns false because its based on 'some', and there are no items to compare, so false is implied. deep-equal((), ()) returns true because its based on every, which in universal quantification is a "vacuous truth" (I googled it :) -- Andrew Welch http://andrewjwelch.com
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