Suggestion: Operator `in` for slices

[Era Scarecrow]

On Tuesday, 21 December 2021 at 17:00:49 UTC, Steven 
Schveighoffer wrote:
> One thing not really being discussed is that there is a 
> difference between "some library" defining slow `in` operators, 
> or slow `opIndex`, and dlang/Phobos doing it.
>
> D picked the path of trying to ensure complexity consistency 
> for `in`, but it's more of a stylistic rule, not necessarily a 
> requirement.

  Then maybe we in should be implemented; Have it check if you 
have it sorted (*unless you do assumesorted template*). If it is 
sorted naturally use BinarySearch, and if not it would probably 
do a linear search **BUT** give a warning message and file/line 
number so it can be fixed/traced? (*Or just make it have to be 
Binary Search and asserts out if it isn't sorted*)

  As for bool vs pointer return... probably return a pointer as 
that can easily be tested as bool for no extra cost.