[Issue 13936] groupBy must be redone

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13936

--- Comment #28 from hsteoh at quickfur.ath.cx ---
Another note: your current implementation looks like it could be easily
extended to handle non-equivalence predicates. All you need to do is to
evaluate the predicate on adjacent elements vs. with the head of the group
(IOW, just advance groupStart each time in Group.popFront). I doubt it would
cause too much performance hit.

--