Kotlin - List Ops Complete

kotlin/list-ops/src/main/kotlin/ListExt.kt

@@ -1,17 +1,41 @@
 fun <T> List<T>.customAppend(inpList: List<T>): List<T>{
-    return emptyList<T>()
+    val newList = mutableListOf<T>()
+
+    newList.addAll(this)
+
+    newList.addAll(inpList)
+
+    return newList
 }
 
 fun <T> List<List<T>>.customConcat(): List<T>{
-    return emptyList<T>()
+    val newList = mutableListOf<T>()
+
+    this.forEach { newList.addAll(it) }
+
+    return newList
 }
 
 fun <T> List<T>.customFilter(inpFunc: (T) -> Boolean): List<T>{
-    return emptyList<T>()
+    val newList = mutableListOf<T>()
+
+    for (i in this){
+        if (inpFunc(i)){
+            newList.add(i)
+        }
+    }
+
+    return newList
 }
 
 fun <T, R> List<T>.customMap(inpFunc: (T) -> R): List<R>{
-    return emptyList<R>()
+    val newList = mutableListOf<R>()
+
+    for (i in this){
+        newList.add(inpFunc(i))
+    }
+
+    return newList
 }
 
 val <T> List<T>.customSize: Int
@@ -24,14 +48,28 @@ val <T> List<T>.customSize: Int
     }
 
 
-fun <T> List<T>.customReverse(): List<T>{
-    return emptyList<T>()
-}
-
 fun <T, R> List<T>.customFoldLeft(acc: R, inpFunc: (R, T) -> R): R {
-    return inpFunc(acc, acc as T)
+    if (this.isEmpty()){
+        return acc
+    }
+
+    return this.drop(1).customFoldLeft(inpFunc(acc, this.first()), inpFunc)
 }
 
 fun <T, R> List<T>.customFoldRight(acc: R, inpFunc: (T, R) -> R): R{
-    return inpFunc(acc as T, acc)
+    if (this.isEmpty()){
+        return acc
+    }
+
+    return inpFunc(first(), this.drop(1).customFoldRight(acc, inpFunc))
+}
+
+fun <T> List<T>.customReverse(): List<T>{
+    val newList = mutableListOf<T>()
+
+    for (i in this){
+        newList.add(0, i)
+    }
+
+    return newList
 }

kotlin/list-ops/src/test/kotlin/ListExtensionsTest.kt

@@ -14,7 +14,6 @@ class ListExtensionsTest {
                 emptyList<Int>().customAppend(emptyList()))
     }
 
-    @Ignore
     @Test
     fun testAppendingNonEmptyListOnEmptyList() {
         assertEquals(
@@ -22,7 +21,6 @@ class ListExtensionsTest {
                 emptyList<Char>().customAppend(listOf('1', '2', '3', '4')))
     }
 
-    @Ignore
     @Test
     fun testAppendingNonEmptyListOnNonEmptyList() {
         assertEquals(
@@ -30,7 +28,6 @@ class ListExtensionsTest {
                 listOf("1", "2").customAppend(listOf("2", "3", "4", "5")))
     }
 
-    @Ignore
     @Test
     fun testConcatOnEmptyListOfLists() {
         assertEquals(
@@ -38,7 +35,6 @@ class ListExtensionsTest {
                 emptyList<List<Int>>().customConcat())
     }
 
-    @Ignore
     @Test
     fun testConcatOnNonEmptyListOfLists() {
         assertEquals(
@@ -46,7 +42,6 @@ class ListExtensionsTest {
                 listOf(listOf('1', '2'), listOf('3'), emptyList(), listOf('4', '5', '6')).customConcat())
     }
 
-    @Ignore
     @Test
     fun testFilteringEmptyList() {
         assertEquals(
@@ -54,7 +49,6 @@ class ListExtensionsTest {
                 emptyList<Int>().customFilter { it % 2 == 1 })
     }
 
-    @Ignore
     @Test
     fun testFilteringNonEmptyList() {
         assertEquals(
@@ -72,7 +66,6 @@ class ListExtensionsTest {
         assertEquals(4, listOf("one", "two", "three", "four").customSize)
     }
 
-    @Ignore
     @Test
     fun testTransformingEmptyList() {
         assertEquals(
@@ -80,7 +73,6 @@ class ListExtensionsTest {
                 emptyList<Int>().customMap { it -> it + 1 })
     }
 
-    @Ignore
     @Test
     fun testTransformingNonEmptyList() {
         assertEquals(
@@ -88,7 +80,6 @@ class ListExtensionsTest {
                 listOf(1, 3, 5, 7).customMap { it -> it + 1 })
     }
 
-    @Ignore
     @Test
     fun testFoldLeftOnEmptyList() {
         assertEquals(
@@ -96,7 +87,6 @@ class ListExtensionsTest {
                 emptyList<Int>().customFoldLeft(2.0, Double::times))
     }
 
-    @Ignore
     @Test
     fun testFoldLeftWithDirectionIndependentOperationOnNonEmptyList() {
         assertEquals(
@@ -104,7 +94,6 @@ class ListExtensionsTest {
                 listOf(1, 2, 3, 4).customFoldLeft(5, Int::plus))
     }
 
-    @Ignore
     @Test
     fun testFoldLeftWithDirectionDependentOperationOnNonEmptyList() {
         assertEquals(
@@ -112,7 +101,6 @@ class ListExtensionsTest {
                 listOf(2, 5).customFoldLeft(5, Int::div))
     }
 
-    @Ignore
     @Test
     fun testFoldRightOnEmptyList() {
         assertEquals(
@@ -120,7 +108,6 @@ class ListExtensionsTest {
                 emptyList<Double>().customFoldRight(2.0, Double::times))
     }
 
-    @Ignore
     @Test
     fun testFoldRightWithDirectionIndependentOperationOnNonEmptyList() {
         assertEquals(
@@ -128,7 +115,6 @@ class ListExtensionsTest {
                 listOf(1, 2, 3, 4).customFoldRight(5, Int::plus))
     }
 
-    @Ignore
     @Test
     fun testFoldRightWithDirectionDependentOperationOnNonEmptyList() {
         assertEquals(
@@ -136,7 +122,6 @@ class ListExtensionsTest {
                 listOf(2, 5).customFoldRight(5, Int::div))
     }
 
-    @Ignore
     @Test
     fun testReversingEmptyList() {
         assertEquals(
@@ -144,7 +129,6 @@ class ListExtensionsTest {
                 emptyList<Int>().customReverse())
     }
 
-    @Ignore
     @Test
     fun testReversingNonEmptyList() {
         assertEquals(