added a couple of helper functions to make it easier to compare values, implement Comparable and create Comparators

libraries/stdlib/test/CompareTest.kt

@@ -0,0 +1,40 @@
+package test
+
+import org.junit.Test
+
+import kotlin.test.*
+
+class Item(val name: String, val rating: Int)
+
+/**
+ */
+class CompareTest {
+    val v1 = Item("wine", 9)
+    val v2 = Item("beer", 10)
+
+    Test fun compareByNameFirst() {
+        val diff = compareBy(v1, v2, {(i: Item) -> i.name}, {(i: Item) -> i.rating})
+        assertTrue(diff > 0)
+    }
+
+    Test fun compareByRatingFirst() {
+        val diff = compareBy(v1, v2, {(i: Item) -> i.rating}, {(i: Item) -> i.name})
+        assertTrue(diff < 0)
+    }
+
+    Test fun compareSameObjectsByRatingFirst() {
+        val diff = compareBy(v1, v1, {(i: Item) -> i.rating}, {(i: Item) -> i.name})
+        assertTrue(diff == 0)
+    }
+
+    Test fun createComparator() {
+        val c = comparator({(i: Item) -> i.rating}, {(i: Item) -> i.name})
+        println("Created comparator $c")
+/*
+        val items = arrayList(v1, v2)
+        items.sort(c)
+        println("Sorted list in rating order $items")
+*/
+
+    }
+}