From: Just Another Victim of the Ambient Morality <ihatespam@...>
Date: 2006-08-10T08:55:12+09:00
Subject: Re: Enumerable#all? and empty arrays


"Andre Nathan" <andre@digirati.com.br> wrote in message 
news:1155141696.24603.43.camel@andre.mz.digirati.com.br...
> Hello
>
> I found this to be somewhat amusing:
>
>>> a = []
> => []
>>> a.all?
> => true
>>> a.all? { |i| i == 10 }
> => true
>
> Is there any reasoning for Enumerable#all? to always return true for
> empty arrays?

    It's mathematically consistent.

    You may be surprised to hear this but mathematicians are generally 
optimists.  Thus, if a condition is "vacuously satisfied," then we generally 
say the condition is true...