Maxim Shafirov
83 lines
2.2 KiB
Kotlin
83 lines
2.2 KiB
Kotlin
package kotlin
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/**
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* Get the first element in the list or throws [[EmptyIterableException]] if list is empty.
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*/
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public inline fun <T> List<T>.first() : T {
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return if (size() > 0) get(0) else throw EmptyIterableException(this)
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}
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/**
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* Get the first element in the list or *null* if list is empty.
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*/
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public inline fun <T:Any> List<T>.firstOrNull() : T? {
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return if (size() > 0) get(0) else null
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}
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/**
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* Get the last element in the list or throws [[EmptyIterableException]] if list is empty.
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*/
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public inline fun <T> List<T>.last() : T {
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val s = size()
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return if (s > 0) get(s - 1) else throw EmptyIterableException(this)
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}
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/**
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* Get the last element in the list or *null* if list is empty.
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*/
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public inline fun <T:Any> List<T>.lastOrNull() : T? {
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val s = size()
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return if (s > 0) get(s - 1) else null
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}
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public inline fun <T> List<T>.forEachWithIndex(operation : (Int, T) -> Unit) {
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for (index in indices) {
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operation(index, get(index))
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}
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}
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/**
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* Folds all elements from right to left with the *initial* value to perform the operation on sequential pairs of elements
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*/
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public inline fun <T, R> List<T>.foldRight(initial: R, operation: (T, R) -> R) : R {
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var r = initial
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var index = size - 1
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while (index >= 0) {
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r = operation(get(index--), r)
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}
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return r
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}
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/**
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* Applies binary operation to all elements of iterable, going from right to left.
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* Similar to foldRight function, but uses the last element as initial value
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*/
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public inline fun <T> List<T>.reduceRight(operation: (T, T) -> T) : T {
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var index = size - 1
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if (index < 0) {
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throw UnsupportedOperationException("Empty iterable can't be reduced")
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}
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var r = get(index--)
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while (index >= 0) {
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r = operation(get(index--), r)
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}
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return r
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}
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/**
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* Returns a original Iterable containing all the non-*null* elements, throwing an [[IllegalArgumentException]] if there are any null elements
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*/
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public inline fun <T:Any> List<T?>.requireNoNulls() : List<T> {
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for (element in this) {
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if (element == null) {
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throw IllegalArgumentException("null element found in $this")
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}
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}
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return this as List<T>
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}
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