“in ..” syntax considered harmful?

Unlike my expectation, a in b .. c converted to a <= b && b <= c, it seems it is not implemented as what I said.

What I wrote at first was

when(a.compareTo(b)) { in 1..INT.MAX_VALUE -> //do something else -> // do other things } 

and I found out Integer.valueOf and IntIterator.next consume every CPU power after profiled my code.

After googing I realized kotlin permits operator < or > unlike Java, and the revised one

when { a > b -> // do something else -> // do other things } 

makes the program faster dramatically 🙂