From 019962b6546d110852a17c7be25274d1ccc6793d Mon Sep 17 00:00:00 2001
From: Alexander Zolotov <Alexander.Zolotov@jetbrains.com>
Date: Sun, 24 Jun 2012 17:56:46 +0400
Subject: [PATCH] Add sortBy method for interables

---
 .../stdlib/src/kotlin/JLangIterablesSpecial.kt      | 13 +++++++++++++
 libraries/stdlib/test/CollectionTest.kt             | 11 +++++++++++
 2 files changed, 24 insertions(+)

diff --git a/libraries/stdlib/src/kotlin/JLangIterablesSpecial.kt b/libraries/stdlib/src/kotlin/JLangIterablesSpecial.kt
index adc2be1e622..fab0cfed4e9 100644
--- a/libraries/stdlib/src/kotlin/JLangIterablesSpecial.kt
+++ b/libraries/stdlib/src/kotlin/JLangIterablesSpecial.kt
@@ -71,6 +71,19 @@ public fun <T> java.lang.Iterable<T>.last() : T {
   return last;
 }
 
+/**
+ * Copies all elements into a [[List]] and sorts it by value of compare_function(element)
+ *
+ * E.g. arrayList("two" to 2, "one" to 1).sortBy({it._2}) returns list sorted by second element of tuple
+ *
+ * @includeFunctionBody ../../test/CollectionTest.kt sortBy
+ */
+public inline fun <in T, R: Comparable<in R>> java.lang.Iterable<T>.sortBy(f: (T) -> R): java.util.List<T> {
+    val sortedList = this.toList()
+    java.util.Collections.sort(sortedList, comparator {(x, y) -> f(x).compareTo(f(y))})
+    return sortedList
+}
+
 /**
  * Checks if collection contains given item.
  *
diff --git a/libraries/stdlib/test/CollectionTest.kt b/libraries/stdlib/test/CollectionTest.kt
index d80743a32d2..030d5f081d9 100644
--- a/libraries/stdlib/test/CollectionTest.kt
+++ b/libraries/stdlib/test/CollectionTest.kt
@@ -445,6 +445,17 @@ class CollectionTest {
         //    assertFalse(IterableWrapper(linkedList<Int>()).contains(15))
     }
 
+    test fun sortBy() {
+        expect(arrayList("two" to 2, "three" to 3)) {
+            arrayList("three" to 3, "two" to 2).sortBy { it._2 }
+        }
+        expect(arrayList("three" to 3, "two" to 2)) {
+            arrayList("three" to 3, "two" to 2).sortBy { it._1 }
+        }
+        expect(arrayList("two" to 2, "three" to 3)) {
+            arrayList("three" to 3, "two" to 2).sortBy { it._1.length }
+        }
+    }
 
     class IterableWrapper<T>(collection : java.lang.Iterable<T>) : java.lang.Iterable<T> {
         private val collection = collection