Add second(), third(), forth(), fifth() and penultimate()

Author: JavierSegoviaCordoba

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## [Unreleased]
 
 ### Added
+- `second()`, `third()`, `forth()`, `fifth()` and `penultimate()`
 
 ### Changed
 

kotlin-stdlib/api/kotlin-stdlib.api

@@ -141,6 +141,16 @@ public final class com/javiersc/kotlin/stdlib/AnsiColorsKt {
 	public static final fun ansiColor (Ljava/lang/String;Lcom/javiersc/kotlin/stdlib/AnsiColor;)Ljava/lang/String;
 }
 
+public final class com/javiersc/kotlin/stdlib/CollectionsKt {
+	public static final fun fifth (Ljava/lang/Iterable;)Ljava/lang/Object;
+	public static final fun forth (Ljava/lang/Iterable;)Ljava/lang/Object;
+	public static final fun getIndex (Ljava/lang/Iterable;I)Ljava/lang/Object;
+	public static final fun penultimate (Ljava/lang/Iterable;)Ljava/lang/Object;
+	public static final fun second (Ljava/lang/Iterable;)Ljava/lang/Object;
+	public static final fun third (Ljava/lang/Iterable;)Ljava/lang/Object;
+	public static final fun throwNoSuchElementException (I)V
+}
+
 public final class com/javiersc/kotlin/stdlib/StringsKt {
 	public static final fun remove (Ljava/lang/String;Ljava/lang/String;Z)Ljava/lang/String;
 	public static synthetic fun remove$default (Ljava/lang/String;Ljava/lang/String;ZILjava/lang/Object;)Ljava/lang/String;

kotlin-stdlib/build.gradle.kts

@@ -34,6 +34,15 @@ kotlin {
     watchosArm64()
     watchosSimulatorArm64()
     watchosX64()
+
+    sourceSets {
+        commonTest {
+            dependencies {
+                implementation(libs.jetbrains.kotlin.kotlinTest)
+//                implementation(libs.kotest.kotestAssertionsCore)
+            }
+        }
+    }
 }
 
 tasks.withType<DokkaTask> {

kotlin-stdlib/commonMain/kotlin/Collections.kt

@@ -0,0 +1,52 @@
+@file:Suppress("MagicNumber")
+
+package com.javiersc.kotlin.stdlib
+
+public inline fun <T> Iterable<T>.second(): T = getIndex(2)
+
+public inline fun <T> Iterable<T>.third(): T = getIndex(3)
+
+public inline fun <T> Iterable<T>.forth(): T = getIndex(4)
+
+public inline fun <T> Iterable<T>.fifth(): T = getIndex(5)
+
+public inline fun <T> Iterable<T>.penultimate(): T {
+    return when (this) {
+        is List -> this[size - 2]
+        else -> {
+            val iterator = iterator()
+            if (!iterator.hasNext()) throw NoSuchElementException("Collection is empty.")
+            iterator.next()
+            if (!iterator.hasNext()) {
+                throw NoSuchElementException("Collection size is lower than 2.")
+            }
+            var penultimate: T = iterator.next()
+            while (iterator.hasNext()) {
+                val next: T = iterator.next()
+                if (iterator.hasNext()) penultimate = next
+            }
+            return penultimate
+        }
+    }
+}
+
+public inline fun <T> Iterable<T>.getIndex(index: Int): T {
+    return when (this) {
+        is List -> this[index - 1]
+        else -> {
+            val iterator = iterator()
+            if (!iterator.hasNext()) throwNoSuchElementException(index)
+            var value: T = iterator.next()
+
+            for (i in 0 until index - 1) {
+                if (!iterator.hasNext()) throwNoSuchElementException(index)
+                else value = iterator.next()
+            }
+            value
+        }
+    }
+}
+
+@PublishedApi
+internal fun throwNoSuchElementException(size: Int): Unit =
+    throw NoSuchElementException("Collection size is lower than $size.")

kotlin-stdlib/commonTest/kotlin/CollectionsTest.kt

@@ -0,0 +1,15 @@
+@file:Suppress("MagicNumber")
+
+import com.javiersc.kotlin.stdlib.second
+import kotlin.test.Test
+import kotlin.test.assertTrue
+
+class CollectionsTest {
+
+    private val numbers = listOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
+
+    @Test
+    fun collection_second() {
+        assertTrue { numbers.second() == 2 }
+    }
+}