Fitness proportionate selection in Kotlin (RouletteWheel)

RouletteWheel.kt

inline fun <T> List<T>.selectRouletteWheelWithMinimum(
    min: Double = 100.0,
    sum: (T) -> Double
): T? {
    if(isEmpty()) return null

    val total = reversed().sumByDouble(sum)

    val random = (Math.random() * if(total > min) total else min)

    if(random > total) return null

    return rouletteWheelFirstGreaterThemRandom(random, sum)
}

inline fun <T> List<T>.selectRouletteWheel(
    sum: (T) -> Double
): T {
    val reversed = reversed()
    val total = reversed.sumByDouble(sum)

    val random = Math.random() * total

    return reversed.rouletteWheelFirstGreaterThemRandom(random, sum)
}

inline fun <T> Iterable<T>.rouletteWheelFirstGreaterThemRandom(
    random: Double,
    sum: (T) -> Double
): T {
    var partialSum = 0.0
    return first { current ->
        partialSum += sum(current)

        partialSum >= random
    }
}