From 5db75c993bf98ee1f1d713544963ec67ff3367f9 Mon Sep 17 00:00:00 2001
From: Ilya Gorbunov <ilya.gorbunov@jetbrains.com>
Date: Mon, 26 Dec 2016 22:20:53 +0300
Subject: [PATCH] Introduce array-like list instantiation functions. #KT-14935
 Fixed

---
 .../src/kotlin/collections/Collections.kt     | 20 +++++++++++++++++++
 .../stdlib/test/collections/CollectionTest.kt |  6 ++++++
 2 files changed, 26 insertions(+)

diff --git a/libraries/stdlib/src/kotlin/collections/Collections.kt b/libraries/stdlib/src/kotlin/collections/Collections.kt
index 6c20db08d5a..96cb57725e4 100644
--- a/libraries/stdlib/src/kotlin/collections/Collections.kt
+++ b/libraries/stdlib/src/kotlin/collections/Collections.kt
@@ -104,6 +104,26 @@ public fun <T : Any> listOfNotNull(element: T?): List<T> = if (element != null)
 /** Returns a new read-only list only of those given elements, that are not null.  The returned list is serializable (JVM). */
 public fun <T : Any> listOfNotNull(vararg elements: T?): List<T> = elements.filterNotNull()
 
+/**
+ * Creates a new read-only list with the specified [size], where each element is calculated by calling the specified
+ * [init] function. The [init] function returns a list element given its index.
+ */
+@SinceKotlin("1.1")
+@kotlin.internal.InlineOnly
+public inline fun <T> List(size: Int, init: (index: Int) -> T): List<T> = MutableList(size, init)
+
+/**
+ * Creates a new mutable list with the specified [size], where each element is calculated by calling the specified
+ * [init] function. The [init] function returns a list element given its index.
+ */
+@SinceKotlin("1.1")
+@kotlin.internal.InlineOnly
+public inline fun <T> MutableList(size: Int, init: (index: Int) -> T): MutableList<T> {
+    val list = ArrayList<T>(size)
+    repeat(size) { index -> list.add(init(index)) }
+    return list
+}
+
 /**
  * Returns an [IntRange] of the valid indices for this collection.
  */
diff --git a/libraries/stdlib/test/collections/CollectionTest.kt b/libraries/stdlib/test/collections/CollectionTest.kt
index 6f301a2d966..8bce7f3ed5b 100644
--- a/libraries/stdlib/test/collections/CollectionTest.kt
+++ b/libraries/stdlib/test/collections/CollectionTest.kt
@@ -24,6 +24,12 @@ import kotlin.comparisons.*
 
 class CollectionTest {
 
+    @Test fun createListWithInit() {
+        val list = List(3) { index -> "x".repeat(index + 1) }
+        assertEquals(3, list.size)
+        assertEquals(listOf("x", "xx", "xxx"), list)
+    }
+
     @Test fun joinTo() {
         val data = listOf("foo", "bar")
         val buffer = StringBuilder()