Provide minWith and maxWith to find maximum and minimum values according to the given comparator.

#KT-9002 Fixed

libraries/stdlib/test/OrderingTest.kt

@@ -10,6 +10,8 @@ data class Item(val name: String, val rating: Int) : Comparable<Item> {
     }
 }
 
+val STRING_CASE_INSENSITIVE_ORDER: Comparator<String> = compareBy { it: String -> it.toUpperCase() }.thenBy { it.toLowerCase() }.thenBy { it }
+
 class OrderingTest {
     val v1 = Item("wine", 9)
     val v2 = Item("beer", 10)

libraries/stdlib/test/collections/ArraysTest.kt

@@ -1,6 +1,7 @@
 package test.collections
 
 import test.collections.behaviors.listBehavior
+import test.compare.STRING_CASE_INSENSITIVE_ORDER
 import java.util.*
 import kotlin.test.*
 import org.junit.Test as test
@@ -146,6 +147,28 @@ class ArraysTest {
         expect('b', { charArrayOf('a', 'b').max() })
     }
 
+    @test fun minWith() {
+        assertEquals(null, arrayOf<Int>().minWith(naturalOrder()) )
+        assertEquals("a", arrayOf("a", "B").minWith(STRING_CASE_INSENSITIVE_ORDER))
+    }
+
+    @test fun minWithInPrimitiveArrays() {
+        expect(null, { intArrayOf().minWith(naturalOrder()) })
+        expect(1, { intArrayOf(1).minWith(naturalOrder()) })
+        expect(4, { intArrayOf(2, 3, 4).minWith(compareBy { it % 4 }) })
+    }
+
+    @test fun maxWith() {
+        assertEquals(null, arrayOf<Int>().maxWith(naturalOrder()) )
+        assertEquals("B", arrayOf("a", "B").maxWith(STRING_CASE_INSENSITIVE_ORDER))
+    }
+
+    @test fun maxWithInPrimitiveArrays() {
+        expect(null, { intArrayOf().maxWith(naturalOrder()) })
+        expect(1, { intArrayOf(1).maxWith(naturalOrder()) })
+        expect(-4, { intArrayOf(2, 3, -4).maxWith(compareBy { it*it }) })
+    }
+
     @test fun minBy() {
         expect(null, { arrayOf<Int>().minBy { it } })
         expect(1, { arrayOf(1).minBy { it } })

libraries/stdlib/test/collections/CollectionTest.kt

@@ -4,6 +4,7 @@ import java.util.*
 import kotlin.test.*
 import org.junit.Test as test
 import test.collections.behaviors.*
+import test.compare.STRING_CASE_INSENSITIVE_ORDER
 import java.io.Serializable
 
 class CollectionTest {
@@ -496,6 +497,20 @@ class CollectionTest {
         expect(3, { listOf(2, 3).asSequence().max() })
     }
 
+    @test fun minWith() {
+        expect(null, { listOf<Int>().minWith(naturalOrder()) })
+        expect(1, { listOf(1).minWith(naturalOrder()) })
+        expect("a", { listOf("a", "B").minWith(STRING_CASE_INSENSITIVE_ORDER) })
+        expect("a", { listOf("a", "B").asSequence().minWith(STRING_CASE_INSENSITIVE_ORDER) })
+    }
+
+    @test fun maxWith() {
+        expect(null, { listOf<Int>().maxWith(naturalOrder()) })
+        expect(1, { listOf(1).maxWith(naturalOrder()) })
+        expect("B", { listOf("a", "B").maxWith(STRING_CASE_INSENSITIVE_ORDER) })
+        expect("B", { listOf("a", "B").asSequence().maxWith(STRING_CASE_INSENSITIVE_ORDER) })
+    }
+
     @test fun minBy() {
         expect(null, { listOf<Int>().minBy { it } })
         expect(1, { listOf(1).minBy { it } })