I'd like to check if a range is within another range, ie

i-2..i+2 in wd.indices

there's two possible answers, both reasonable for different purposes:

this.start <= other.endInclusive && this.endInclusive >= other.start
this.start >= other.start && this.endInclusive <= other.endInclusive

plus additional considerations around what the result should be with empty ranges

I don't see any reason why one would interpret this as the first option

I'm doing exactly this atm

Thinking how operator

in

is implemented in Kotlin, it seems to imply that some element is contained in some *set*(collection), not subset. In java, there is

containsAll

, not

contains

.

This would work but would currently be too expensive:

wd.indices.toSet().containsAll((i-2..i+2).toSet())

That's only because toSet() creates a LinkedHashSet. Perhaps it could be optimized to create a specialized Set that just keeps the range as its only property and whose

contains

method just forwards to the range, and defines a suitably specialized

containsAll

. Then the above code would have good performance. Or perhaps just a new

containsAll

method on ranges.

Yes, sorry for not being clear. I meant

contains

(which corresponds to

in

) does not work for set-to-set. (like

Set.contains(Set)

)