Contains none test
Learn how to check if a collection has no elements in common with another.
This test checks whether one collection contains none of the elements of another. It is the opposite of the contains all test.
This operation corresponds to the mathematical concepts of superset and subset. Specifically, it checks whether the collection 𝐴 is not a superset of 𝐵 (𝐴 ⊉ 𝐵) or, conversely, whether 𝐵 is not a subset of 𝐴 (𝐵 ⊈ 𝐴).
Note that the result is always false if the second collection is empty, because the empty set is a subset of every set. This is different from the contains neither test, which returns true in this case, as it operates on the idea of intersection rather than subset.
Technically, yes. Since there are no unicorns in the room, there's no unicorn that isn't shining. Logic is fun, isn't it?
Also, keep in mind that neither the order nor duplicate elements affect the result since collections are treated as sets.
Syntax
This test has the following syntax:
/*<collection>*/ contains none of /*<collection>*/
Alternatively, you can use the following syntax:
/*<collection>*/ includes none of /*<collection>*/
Both forms have the same semantics. You can use whichever makes your query more expressive and easier to read.
You can negate the test to verify the contrary:
/*<collection>*/ does not contain none of /*<collection>*/
The same applies to the alternative syntax:
/*<collection>*/ does not include none of /*<collection>*/
However, consider using the contains all test instead of negating, as it is more expressive and easier to understand.
Parameters
These are the supported parameters:
- collection
The collection to check.
- subset
The collection whose elements must not be contained in the other collection.
Examples
Here is an example of a collection that contains none of the elements of another collection:
["a", "b", "c"] contains none of ["d", "e", "f"] // true
And here is a counterexample:
["a", "b", "c"] contains none of ["a", "d", "e"] // false
To negate the test, you can write:
["a", "b", "c"] does not contain none of ["d", "e", "f"] // false
If the second collection is empty, the result is always false:
["a", "b", "c"] contains none of [] // false