[Tutor] Built In Functions

[Danny Yoo]

>>>> all('')
> True
>
> Actually the last one surprised me. I expected false. So maybe a resident
> guru can explain that anomaly... I assume it works on the basis of testing
> until it finds a false and so an empty sequence
> always returns true...

The term you're thinking of is "vacuous truth"

    http://en.wikipedia.org/wiki/Vacuous_truth

It's true that, for the empty collection, every element is true, since
there are no counterexamples.