Add baisc Array extensions

README.md

@@ -217,3 +217,16 @@ byteBuffer.applyIf(shouldReadInt) { getInt() }
 #### [Services](src/main/kotlin/pw/forst/katlib/Services.kt)
 
 * `TemporalProvider` - Interface providing access to current time via `now` method, very useful when mocking
+
+#### [Array Extensions](src/main/kotlin/pw/forst/katlib/ArrayExtensions.kt)
+
+* `buildArray(builderAction: MutableList<E>.() -> Unit): Array<E>` - builds a new Array by populating a MutableList using the given builderAction and returning an Array with the same elements
+* `Array<out T>.map(transform: (T) -> R): Array<R>` - Returns an array containing the results of applying the given transform function to each element in the original array
+* `Array<out T>.mapIndexed(transform: (index: Int, T) -> R): Array<R>` - returns an array containing the results of applying the given transform function to each element and its index in the original array
+* `Array<out T>.filter(predicate: (T) -> Boolean): Array<T>` - returns an array containing only elements matching the given predicate
+* `Array<out T>.filterNot(predicate: (T) -> Boolean): Array<T>` - returns an array containing all elements not matching the given predicate
+* `Array<out T>.filterIndexed(predicate: (index: Int, T) -> Boolean): Array<T>` - returns an array containing only elements matching the given predicate
+* `Array<*>.filterIsInstance(): Array<R>` - returns an array containing all elements that are instances of specified type parameter R
+* `Array<out T?>.filterNotNull(): Array<T>` - returns an array containing all elements that are not `null`
+* `Array<out T>.minus(element: T): Array<T>` - returns an array containing all elements of the original collection without the first occurrence of the given element
+* `Array<out T>.minus(elements: Array<out T>): Array<T>` - returns an array containing all elements of the original collection except the elements contained in the given elements array

src/main/kotlin/pw/forst/katlib/ArrayExtensions.kt

@@ -0,0 +1,69 @@
+package pw.forst.katlib
+
+import kotlin.experimental.ExperimentalTypeInference
+
+/**
+ * Builds a new [Array] by populating a [MutableList] using the given [builderAction]
+ * and returning an Array with the same elements.
+ *
+ * The list passed as a receiver to the [builderAction] is valid only inside that function.
+ * Using it outside of the function produces an unspecified behavior.
+ */
+/* 	It uses BuilderInference just like buildList,
+	but it can't use buildLists @WasExperimental(ExperimentalStdlibApi::class) annotation because it's kotlin internal*/
+@Suppress("EXPERIMENTAL_IS_NOT_ENABLED")
+@OptIn(ExperimentalTypeInference::class)
+inline fun <reified E> buildArray(@BuilderInference builderAction: MutableList<E>.() -> Unit) = buildList(builderAction).toTypedArray()
+
+/**
+ * Returns an array containing the results of applying the given [transform] function
+ * to each element in the original array.
+ */
+inline fun <T, reified R> Array<out T>.map(transform: (T) -> R) = mapTo(ArrayList(size), transform).toTypedArray()
+
+/**
+ * Returns an array containing the results of applying the given [transform] function
+ * to each element and its index in the original array.
+ * @param [transform] function that takes the index of an element and the element itself
+ * and returns the result of the transform applied to the element.
+ */
+inline fun <T, reified R> Array<out T>.mapIndexed(transform: (index: Int, T) -> R) = mapIndexedTo(ArrayList(size), transform).toTypedArray()
+
+/**
+ * Returns an array containing only elements matching the given [predicate].
+ */
+inline fun <reified T> Array<out T>.filter(predicate: (T) -> Boolean) = filterTo(ArrayList(), predicate).toTypedArray()
+
+/**
+ * Returns an array containing all elements not matching the given [predicate].
+ */
+inline fun <reified T> Array<out T>.filterNot(predicate: (T) -> Boolean) = filterNotTo(ArrayList(), predicate).toTypedArray()
+
+/**
+ * Returns an array containing only elements matching the given [predicate].
+ * @param [predicate] function that takes the index of an element and the element itself
+ * and returns the result of predicate evaluation on the element.
+ */
+inline fun <reified T> Array<out T>.filterIndexed(predicate: (index: Int, T) -> Boolean) =
+	filterIndexedTo(ArrayList(), predicate).toTypedArray()
+
+/**
+ * Returns an array containing all elements that are instances of specified type parameter R.
+ */
+inline fun <reified R> Array<*>.filterIsInstance() = filterIsInstanceTo(ArrayList<R>()).toTypedArray()
+
+/**
+ * Returns an array containing all elements that are not `null`.
+ */
+inline fun <reified T : Any> Array<out T?>.filterNotNull() = filterNotNullTo(ArrayList<T>()).toTypedArray()
+
+/**
+ * Returns an array containing all elements of the original collection without the first occurrence of the given [element].
+ */
+inline operator fun <reified T> Array<out T>.minus(element: T) = asList<T>().minus(element).toTypedArray()
+
+/**
+ * Returns an array containing all elements of the original collection except the elements contained in the given [elements] array.
+ */
+@Suppress("ConvertArgumentToSet")
+inline operator fun <reified T> Array<out T>.minus(elements: Array<out T>) = asList<T>().minus(elements).toTypedArray()

src/test/kotlin/pw/forst/katlib/ArrayExtensionsTest.kt

@@ -0,0 +1,84 @@
+package pw.forst.katlib
+
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+
+class ArrayExtensionsTest {
+
+	@Test
+	fun `buildArray Test`() {
+		val builtArray = buildArray {
+			for (i in 0 until 100) {
+				add(i)
+			}
+		}
+		val constructedArray = Array(100) { it }
+		assertContentEquals(builtArray, constructedArray)
+	}
+
+	@Test
+	fun `Array map Test`() {
+		val mappedArray = Array(100) { it }.map { it * 2 }
+		val constructedArray = Array(100) { it * 2 }
+		assertContentEquals(mappedArray, constructedArray)
+	}
+
+	@Test
+	fun `Array mapIndexed Test`() {
+		val mappedArray = Array(100) { 0 }.mapIndexed { index: Int, _: Int -> index }
+		val constructedArray = Array(100) { it }
+		assertContentEquals(mappedArray, constructedArray)
+	}
+
+	@Test
+	fun `Array filter Test`() {
+		val filteredArray = Array(100) { it }.filter { it % 2 == 0 }
+		val constructedArray = Array(50) { it * 2 }
+		assertContentEquals(filteredArray, constructedArray)
+	}
+
+	@Test
+	fun `Array filterNot Test`() {
+		val filteredArray = Array(100) { it }.filterNot { it % 2 != 0 }
+		val constructedArray = Array(50) { it * 2 }
+		assertContentEquals(filteredArray, constructedArray)
+	}
+
+	@Test
+	fun `Array filterIndexed Test`() {
+		val filteredArray = Array(100) { it }.filterIndexed { index, _ -> index % 2 == 0 }
+		val constructedArray = Array(50) { it * 2 }
+		assertContentEquals(filteredArray, constructedArray)
+	}
+
+	@Test
+	fun `Array filterIsInstance Test`() {
+		val filteredArray = arrayOf<Number>(0, 1, 0f, 0.0, 1L).filterIsInstance<Int>()
+		val constructedArray = Array(2) { it }
+		assertContentEquals(filteredArray, constructedArray)
+	}
+
+	@Test
+	fun `Array filterNotNull Test`() {
+		val filteredArray = arrayOf(null, 0, 1, null).filterNotNull()
+		val constructedArray = Array(2) { it }
+		assertContentEquals(filteredArray, constructedArray)
+	}
+
+	@Test
+	fun `Array minus element Test`()
+	{
+		val arrayA = Array(100) { it }
+		val arrayB = Array(100) { it + 200}
+		val combinedArray = arrayA + arrayB
+		assertContentEquals(arrayA, combinedArray - arrayB)
+	}
+
+	@Test
+	fun `Array minus elements Test`()
+	{
+		val arrayA = Array(5){it}
+		val arrayB = Array(4){it}
+		assertContentEquals(arrayA - 4, arrayB)
+	}
+}