Bardy's Kotlin collection extensions

collections.kt

// Takes a Map<K, V> and applies the given function to each one of its elements, returning a new
// Map<K1, V1> with the transformed key-value pairs
fun <K, V, K1, V1> Map<K, V>.transform(function: (Map.Entry<K, V>) -> Pair<K1, V1>): Map<K1, V1> {
    val temp = mutableMapOf<K1, V1>()
    for (entry in this) {
        temp += function(entry)
    }
    return temp
}

// Mirror of Kotlin's sumBy that uses longs instead of integers
fun <T> Iterable<T>.sumBy(selector: (T) -> Long): Long {
    var sum = 0L
    for (element in this) {
        sum += selector(element)
    }
    return sum
}