listIterator

import kotlin.math.*
import kotlin.test.*

fun main() { 
   //sampleStart 
   val list = listOf('a', 'b')
val iterator = list.listIterator()

// "Cursor" is at the beginning of the list,
// so there is no previous element, only a next one
println("iterator.hasPrevious() is ${iterator.hasPrevious()}") // false
println("iterator.hasNext() is ${iterator.hasNext()}") // true

// Let's scan the list in a forward direction
println(iterator.next()) // a
println(iterator.next()) // b

// Cursor is past the end of the list,
// so there is no next element, only a previous one
println("iterator.hasPrevious() is ${iterator.hasPrevious()}") // true
println("iterator.hasNext() is ${iterator.hasNext()}") // false

// Let's scan the list backwards, starting from the end
println(iterator.previous()) // b
println(iterator.previous()) // a

// We ran out of elements
// iterator.previous() // will fail with NoSuchElementException

// Empty list has an empty iterator
val emptyListIterator = emptyList<String>().listIterator()
println("emptyListIterator.hasNext() is ${emptyListIterator.hasNext()}") // false
println("emptyListIterator.hasPrevious() is ${emptyListIterator.hasPrevious()}") // false 
   //sampleEnd
}

import kotlin.math.*
import kotlin.test.*

fun main() { 
   //sampleStart 
   val list = listOf('a', 'b', 'c')

// The iterator will scan elements starting from 'c' (the element at the index = 2)
val sublistIterator = list.listIterator(index = 2)
// However, previous elements are also accessible
println("sublistIterator.hasPrevious() is ${sublistIterator.hasPrevious()}") // true
// One step forward
println(sublistIterator.next()) // c
// Two steps backward
println(sublistIterator.previous()) // c
println(sublistIterator.previous()) // b

// If the index is equal to the length of the list,
// the iterator's "cursor" will point past the last element and only previous elements
// will be accessible
val pastLastIterator = list.listIterator(index = 3)
println("pastLastIterator.hasPrevious() is ${pastLastIterator.hasPrevious()}") // true
println("pastLastIterator.hasNext() is ${pastLastIterator.hasNext()}") // false
println(pastLastIterator.previous()) // c
println(pastLastIterator.previous()) // b

// It's an error to use indices outside of list bounds
// list.listIterator(-1) // will fail with IndexOutOfBoundsException
// list.listIterator(list.size + 1) // will fail with IndexOutOfBoundsException 
   //sampleEnd
}