Is Kotlin's range checking is efficent?

Issue

In Kotlin

val x = 50000
if (x in 1..100000) {
    println(x)
}

I think the above code readability is better than code with inequality. But I wonder the performence of that code is also good.

If it literally iterate 100000 times, it seems too stupid.

Is it equal to (1 <= x && x <= 100000) for performance?

Solution

The .. operator calls the rangeTo operator function, which creates a IntRange object. The in operator then calls the contains operator function, which is implemented as:

public operator fun contains(value: T): Boolean = value >= start && value <= endInclusive

Therefore, it does not loop 100000 times, and it is the same as

1 <= x && x <= 100000

except that it also creates a new IntRange object, which won't really matter in the grand scheme of things.

Answered By - Sweeper