From: "alexeymuranov (Alexey Muranov)" <redmine@...>
Date: 2013-08-03T05:22:19+09:00
Subject: [ruby-core:56343] [CommonRuby - Feature #8723] Array.any? predicate returns true for empty array.


Issue #8723 has been updated by alexeymuranov (Alexey Muranov).


nurettin (Nurettin Onur TUGCU) wrote:
> Yes, I meant for .all? (wasn't able to edit) and the behavior is correct according to docs, and incorrect according to my interpretation of sets. (can a predicate be true when you have empty set?)

[].any? { |x| predicate(x) }

means in human/mathematical language: "there exists x in [] such that predicate(x) is true", this is false because there are not elements in [].

[].all? { |x| predicate(x) }

means: "for every x in [], predicate(x) is true", this is true because there are not elements in [].

If you have no children, it is true that all your children are redhead.
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Feature #8723: Array.any? predicate returns true for empty array.
https://bugs.ruby-lang.org/issues/8723#change-40836

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.


-- 
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