On 3 October 2011 15:15, Wolfgang Laun <wolfgang.laun@xxxxxxxxx> wrote:
> Just think of the universal quantifier "forall" (every $x in X
> satisfies P) as a conjunction over zero or more elements. Its
> initialization must be true (as the initial value for a product must
> be 1). Therefore, the "forall" for an empty set is true.
>
> The quantifier "exists" (some $x in X satisfies P) is a disjunction
> over elements, and its initialization must be false (as the initial
> value for a sum must be 0). Hence, the "exists" for an empty set X is
> false.

Thanks - the 'initialization' is how I saw it - deep-equal() / every
starts from a position of true and looks for a reason to be false, and
 =/some starts from a position of false and looks for a reason to be
true.

Not such faulty logic after all.



-- 
Andrew Welch
http://andrewjwelch.com