Is there a particular reason Kotlin doesn't have i...

# advent-of-code

[Nir]

Is there a particular reason Kotlin doesn't have integer exponentiation? Seems a bit odd to me tbh

[ephemient]

unlike float and bigint, there's a very limited range of exponents before you don't fit into the integer datatype anymore

[Nir]

that is true, but when you want it, it's annoying not to have it

[ephemient]

a modular integer exponentiation function could be more generally useful; python's stdlib pow does that, for example

[ephemient]

if it helps, pow is easy to write the naïve O(x) way,

fun Int.pow(x: Int): Int = (1..x).fold(1) { acc, _ -> acc * this }

and not too hard to write the faster O(log x) way,

fun Int.pow(x: Int): Int = when {
    x < 0 -> throw ArithmeticException("negative exponent")
    x == 0 -> 1
    x == 1 || this == 0 || this == 1 -> this
    this == -1 -> if (x and 1 == 0) 1 else -1
    else -> {
        var r = 1
        var b = this
        var e = x
        while (true) {
            if (e and 1 != 0) r *= b
            e = e ushr 1
            if (e == 0) break
            b *= b
        }
        r
    }
}

[Nir]

I have to say this has come up a bunch of times now, there's been cases where we effectively have base 10 and base 5 numbers, so its just annoying not to have

[Nir]

with base 2 you happen to be able to use shl so you don't miss it as much

[ephemient]

if this is for day 10 part 2, folding is better than exponentiating anyhow, as you don't need extra multiplications