[ruby-core:74023] [Ruby trunk Feature#12110] Create a method to avoid vacuous truth?

Issue #12110 has been updated by Andrew Vit.


Waldyr de Souza wrote:
> I often find myself running into unexpected results when using #all? for example
> 
> `[].all? { |e| false } # => true`

If you expect all false, then why not use `none?`, is it not sufficient?

> Even though it's logically correct could we have a method that express the following?
> 
> `foo.any? && foo.all?(&:bar)`

This also has edge cases, try: `foo = [nil]`

Matthew Kerwin wrote:
> I seem to recall someone suggesting 'any_and_all?' in the past.

This makes sense and it's consistent with `foo.any?(&block) && foo.all?(&block)`

This is still surprising to me, it looks like a contradiction:

```
[].any? #=> false
[].all? #=> true
```

I would expect "all" to be a superset of "any": both should mean "at least one".
Is there a reason for the existing behaviour, or is it just history now?


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Feature #12110: Create a method to avoid vacuous truth?
https://bugs.ruby-lang.org/issues/12110#change-57174

* Author: Waldyr de Souza
* Status: Open
* Priority: Normal
* Assignee: 
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I often find myself running into unexpected results when using #all? for example

[].all? { |e| false } # => true

Even though it's logically correct could we have a method that express the following?

foo.any? && foo.all?(&:bar)



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