From: "nurettin (Nurettin Onur TUGCU)" <onurtugcu@...>
Date: 2013-08-03T19:59:24+09:00
Subject: [ruby-core:56353] [CommonRuby - Feature #8723] Array.any? predicate returns true for empty array.


Issue #8723 has been updated by nurettin (Nurettin Onur TUGCU).


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"Do you agree at least that you initial proposal with assigning false to [].all?{...} was unreasonable?" --alexeymuranov

Well yes, I wanted it to return any false'y value, actually. Including nil. Sorry for not making it clear.

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"They are true because a material conditional is defined to be true when the antecedent is false (or the conclusion is true)." -- http://en.m.wikipedia.org/wiki/Vacuous_truth

OK I agree that the behavior is well-defined in mathematics now. Thanks for the effort everyone.

My confusion arose from the fact that where the mathematical notation for all? would be:

"for all x element of an sequence S where predicate Q is true, the result of all? is true" 

    ���x(x ��� S -> Q)

There were no x where predicate Q was true.

However I see now that Vacuous Truth principle defines that case as well. 

So this makes 

"... but the results of these operations are not undefined." -- Martin

Completely correct. I have no more issue with any? or all?
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Feature #8723: Array.any? predicate returns true for empty array.
https://bugs.ruby-lang.org/issues/8723#change-40848

Author: nurettin (Nurettin Onur TUGCU)
Status: Rejected
Priority: Normal
Assignee: 
Category: 
Target version: 


Are all your children redheaded?
Would this be true if you have no children?
I have no children, therefore none of my children are redheaded.
Therefore 
[].any?{ true } == true makes no sense.
Expected behavior:
[].any?{ true } == false because the array is empty.


-- 
http://bugs.ruby-lang.org/