More uses of operator "in"

[via Digitalmars-d-learn]

On Tuesday, 28 October 2014 at 15:11:01 UTC, Baz wrote:
> On Tuesday, 28 October 2014 at 13:50:24 UTC, Nordlöw wrote:
>> Has there been any proposals/plans to make operator "in" work 
>> for elements in ranges such as
>>
>>    assert('x' in ['x']);
>>
>> I'm missing that Python feature when I work in D.
>
> There is also something similar in Pascal, at the language 
> level. Very handy when working with characters or enums.

AFAIR it's limited to sets in Pascal, where its complexity is 
O(1).