added more DRY compareBy function and helper class

libraries/stdlib/src/kotlin/OrderingJVM.kt

@@ -6,14 +6,14 @@ import java.util.Comparator
 * Helper method for implementing [[Comparable]] methods using a list of functions
 * to calculate the values to compare
 */
-inline fun <T> compareBy(a: T?, b: T?, vararg functions: Function1<T, Any?>): Int {
+inline fun <T> compareBy(a: T?, b: T?, vararg functions: T.() -> Any?): Int {
     require(functions.size > 0)
     if (a === b) return 0
     if (a == null) return - 1
     if (b == null) return 1
     for (fn in functions) {
-        val v1 = fn(a)
-        val v2 = fn(b)
+        val v1 = a.fn()
+        val v2 = b.fn()
         val diff = compareValues(v1, v2)
         if (diff != 0) return diff
     }
@@ -47,12 +47,12 @@ public inline fun <T> compareValues(a: T?, b: T?): Int {
 /**
  * Creates a comparator using the sequence of functions used to calculate a value to compare on
  */
-public inline fun <T> comparator(vararg functions: Function1<T,Any?>): Comparator<T> {
-    return FunctionComparator<T>(functions)
+public inline fun <T> comparator(vararg val functions: T.() -> Any?): Comparator<T> {
+    return FunctionComparator<T>(*functions)
 }
 
 
-private class FunctionComparator<T>(val functions: Array<Function1<T,Any?>>):  Comparator<T> {
+private class FunctionComparator<T>(vararg val functions: T.() -> Any?):  Comparator<T> {
 
     public override fun toString(): String {
         return "FunctionComparator${functions.toList()}"

libraries/stdlib/test/CompareTest.kt

@@ -8,7 +8,7 @@ class Item(val name: String, val rating: Int): Comparable<Item> {
     fun toString() = "Item($name, $rating)"
 
     public override fun compareTo(other: Item): Int {
-        return compareBy(this, other, {it.rating}, {it.name})
+        return compareBy(this, other, { rating }, { name })
     }
 }
 
@@ -22,43 +22,35 @@ class CompareTest {
     }
 
     Test fun compareByNameFirst() {
-        val diff = compareBy(v1, v2, {(i: Item) -> i.name}, {(i: Item) -> i.rating})
+        val diff = compareBy(v1, v2, { name }, { 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 compareByRatingFirstUsingItNotation() {
-        val diff = compareBy(v1, v2, {it.rating}, {it.name})
+        val diff = compareBy(v1, v2, { rating }, { name })
         assertTrue(diff < 0)
     }
 
     Test fun compareSameObjectsByRatingFirst() {
-        val diff = compareBy(v1, v1, {(i: Item) -> i.rating}, {(i: Item) -> i.name})
+        val diff = compareBy(v1, v1, { rating }, { name })
         assertTrue(diff == 0)
     }
 
     Test fun sortUsingComparatorHelperMethod() {
-        val c = comparator<Item>({it.rating}, {it.name})
+        val c = comparator<Item>({ rating }, { name })
         println("Created comparator $c")
 
-        todo {
-        // TODO needs KT-729 before this code works
-            val diff = c.compare(v1, v2)
-            assertTrue(diff < 0)
-            val items = arrayList(v1, v2)
-            items.sort(c)
-            println("Sorted list in rating order $items")
-        }
+        val diff = c.compare(v1, v2)
+        assertTrue(diff < 0)
+        val items = arrayList(v1, v2)
+        items.sort(c)
+        println("Sorted list in rating order $items")
     }
 
     Test fun sortUsingCustomComparator() {
         val c = object : Comparator<Item>{
             override fun compare(o1: Item?, o2: Item?): Int {
-                return compareBy(o1, o2, {(it: Item) -> it.name}, {(it: Item) -> it.rating})
+                return compareBy(o1, o2, { name }, { rating })
             }
             override fun equals(obj: Any?): Boolean {
                 return this == obj

libraries/tools/kdoc/src/main/kotlin/org/jetbrains/kotlin/doc/KDocConfig.kt

@@ -115,7 +115,7 @@ class KDocConfig() {
 
 private class LongestFirstStringComparator() : Comparator<String> {
     public override fun compare(s1: String?, s2: String?): Int {
-        return compareBy(s1, s2, { (s: String) -> s.length() }, { (s: String) -> s })
+        return compareBy(s1, s2, { length() }, { this })
     }
 
     public override fun equals(obj : Any?) : Boolean {