[ruby-core:96321] [Ruby master Feature#16039] Array#contains? to check if one array contains another array

Issue #16039 has been updated by sawa (Tsuyoshi Sawada).


JustJosh (Joshua Stowers) wrote:
> I do not think we should use the name `cover?` because the types of arguments accepted by `Range#cover?` would be incompatible with this use case.
> 
> For example:
> ```ruby
> (1..3).cover?(2) # true
> ```
> But if Array's implementation worked similarly, we would have the following issue:
> ```ruby
> [1, 2, 3].cover?(2) # true by design of Range#cover?
> [1, 2, 3].cover?([2]) # true because all values in argument are also in self
> [1, [2], 3].cover?([2]) # ?
> ```

When the argument is an array, it should be understood as the usual case; i.e., it should be interpreted as the $\subset$ relation. Otherwise, it should be considered as the abbreviated form; in such case, it should be interpreted as the $\in$ relation. So

```ruby
[1, [2], 3].cover?([2])
```

should be unambiguously `false`. To achieve the interpretation that leads to the `true` output, you need to write:

```ruby
[1, [2], 3].cover?([[2])
```

That is exactly analogous to how `Range#cover` works, and there hasn't been a problem there.

----------------------------------------
Feature #16039: Array#contains? to check if one array contains another array
https://bugs.ruby-lang.org/issues/16039#change-83233

* Author: cha1tanya (Prathamesh Sonpatki)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
I woud like to propose `Array#contains?` which will check if the one array is part of another array.
Implementation can be as follows:

```
def contains?(other)
  (other - self).empty?
end
```

Some test cases:

```
[1, 2, 3].contains?([2, 3]) => true
[1, 2, 3].contains?([]) => true
[1, 2, 3].contains?([1, 2, 3, 4]) => false
[].contains?([]) => true
[].contains?([1, 2, 3, 4]) => false
```



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