[KT] Box2d idiomatic - Add an example of an inline function, reified,…

… and crossinline

PiperOrigin-RevId: 733810615

samples/box2d/src/main/kotlin/idiomatic/commonMain/org/jbox2d/common/Mat22.kt

@@ -366,13 +366,7 @@ class Mat22 : Serializable {
   }
 
   override fun equals(other: Any?): Boolean {
-    if (this === other) return true
-    if (other == null) return false
-    if (this::class != other::class) return false
-    if (other !is Mat22) return false
-    if (ex != other.ex) return false
-    if (ey != other.ey) return false
-    return true
+    return equalsOther(other) { ex == it.ex && ey == it.ey }
   }
 
   companion object {

samples/box2d/src/main/kotlin/idiomatic/commonMain/org/jbox2d/common/Mat33.kt

@@ -160,14 +160,7 @@ class Mat33 : Serializable {
   }
 
   override fun equals(other: Any?): Boolean {
-    if (this === other) return true
-    if (other == null) return false
-    if (this::class != other::class) return false
-    if (other !is Mat33) return false
-    if (ex != other.ex) return false
-    if (ey != other.ey) return false
-    if (ez != other.ez) return false
-    return true
+    return equalsOther(other) { ex == it.ex && ey == it.ey && ez == it.ez }
   }
 
   companion object {

samples/box2d/src/main/kotlin/idiomatic/commonMain/org/jbox2d/common/ObjectHelpers.kt

@@ -0,0 +1,33 @@
+/*
+ * ****************************************************************************
+ * Copyright (c) 2013, Daniel Murphy All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification, are permitted
+ * provided that the following conditions are met:
+ * * Redistributions of source code must retain the above copyright notice, this list of conditions
+ *   and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright notice, this list of
+ *   conditions and the following disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
+ * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.jbox2d.common
+
+/**
+ * Compares this instance to [other]. Returns `true` if they are the same instance or if they are
+ * the same type and the comparison function [eq] returns `true`.
+ */
+inline fun <reified T : Any> T.equalsOther(other: Any?, crossinline eq: T.(T) -> Boolean): Boolean {
+  if (this === other) return true
+  if (other == null) return false
+  if (this::class != other::class) return false
+  return eq(other as T)
+}