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amay077/firstIndexOrNull.kt

Created December 6, 2017 05:58
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firstIndexOrNull in Kotlin collections
Raw
firstIndexOrNull.kt
inline fun <T> Iterable<T>.firstIndexOrNull(predicate: (T) -> Boolean): Int? {
return this.mapIndexed { index, place -> Pair(index, place) }
.firstOrNull() { predicate(it.second) }
?.first
}
Raw
usage.kt
val arr = arrayListOf("a", "b", "c")
arr.firstIndexOrNull { it == "b"} // -> 1
arr.firstIndexOrNull { it == "z"} // -> null
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