fun <T> Iterable<T>.indexOf(element: T): Int

Returns first index of element, or -1 if the collection does not contain element.

fun <T> List<T>.indexOf(element: T): Int

Returns first index of element, or -1 if the list does not contain element.

fun <T> Array<out T>.indexOf(element: T): Int

fun ByteArray.indexOf(element: Byte): Int

fun ShortArray.indexOf(element: Short): Int

fun IntArray.indexOf(element: Int): Int

fun LongArray.indexOf(element: Long): Int

fun FloatArray.indexOf(element: Float): Int

fun DoubleArray.indexOf(element: Double): Int

fun BooleanArray.indexOf(element: Boolean): Int

fun CharArray.indexOf(element: Char): Int

Returns first index of element, or -1 if the array does not contain element.